feat(mobile): native-feel sticky top bar + bottom tab nav

Replaces the floating pill nav with persistent mobile chrome that
frames scrolling content the way iOS/Android native apps do.

New components:
- TopBar: brand left, contextual action right (Admin pill for admins,
  bell for saved, Login button when logged out)
- BottomNav: 4-tab fixed nav (Search, Scan [elevated center FAB],
  Saved, Profile). Saved/Profile disabled when logged out, tapping
  opens LoginModal
- icons.jsx: 5 stroke-based SVG icons (Search, Scan, Bell, User, Cog)
  plus Logo; replaces emoji in nav chrome

Behavior changes:
- App.jsx: tracks publicScreen ('home'|'scan'|'search') so BottomNav
  can drive both top-level view + inner screen
- PublicView: screen state lifted to App via props (back-compat
  defaults preserved so existing call sites don't break)
- App.css: old mobile .view-switcher block hidden (replaced by
  BottomNav); .app padding bumped to clear the fixed bottom bar

Desktop (>768px) unchanged — existing centered pill nav still works,
new components hidden via display:none.

Co-Authored-By: Claude <noreply@anthropic.com>

frontend/src/App.css

@@ -290,7 +290,7 @@
 
 @media (max-width: 768px) {
   .app {
-    padding: 1.5rem 1rem calc(5rem + env(safe-area-inset-bottom));
+    padding: 1rem 1rem calc(7rem + env(safe-area-inset-bottom));
   }
 
   .app-header h1 {
@@ -310,25 +310,7 @@
   }
 
   .view-switcher {
-    position: fixed;
-    left: 0.75rem;
-    right: 0.75rem;
-    bottom: calc(0.75rem + env(safe-area-inset-bottom));
-    z-index: 100;
-    width: auto;
-    max-width: 32rem;
-    margin: 0 auto;
-    border-radius: 999px;
-    border: 1px solid var(--border);
-    background: var(--surface);
-    box-shadow:
-      0 10px 30px rgba(28, 25, 23, 0.12),
-      0 2px 6px rgba(28, 25, 23, 0.06);
-    padding: 0.5rem;
-    overflow: visible;
-    justify-content: space-around;
-    align-items: stretch;
-    gap: 0.25rem;
+    display: none; /* ponytail: replaced by BottomNav on mobile */
   }
 
   .view-switcher button {

frontend/src/App.jsx

@@ -5,9 +5,12 @@ import AdminView from './views/AdminView';
 import ProfileView from './views/ProfileView';
 import LoginModal from './components/LoginModal';
 import SavedNotifications from './components/SavedNotifications';
+import TopBar from './components/TopBar';
+import BottomNav from './components/BottomNav';
 
 function App() {
   const [view, setView] = useState('public');
+  const [publicScreen, setPublicScreen] = useState('home'); // 'home' | 'scan' | 'search'
   const [currentUser, setCurrentUser] = useState(null);
   const [authChecked, setAuthChecked] = useState(false);
   const [showLogin, setShowLogin] = useState(false);
@@ -30,6 +33,7 @@ function App() {
     await fetch('/api/auth/logout', { method: 'POST' }).catch(() => {});
     setCurrentUser(null);
     setView('public');
+    setPublicScreen('home');
   }
 
   function handleProfileSaved(updated) {
@@ -55,12 +59,47 @@ function App() {
       <PublicView
         currentUser={currentUser}
         onLoginRequest={() => setShowLogin(true)}
+        screen={publicScreen}
+        onScreenChange={setPublicScreen}
       />
     );
   }
 
+  // ponytail: BottomNav active tab derived from view + publicScreen. Hidden on desktop via CSS.
+  function navActiveTab() {
+    if (view === 'profile') return 'profile';
+    if (view === 'admin') return 'profile'; // no admin tab in bottom nav; profile still highlighted
+    if (publicScreen === 'scan') return 'scan';
+    if (publicScreen === 'search') return 'search';
+    return 'search'; // home → search is the default landing active
+  }
+
+  function handleNavChange(tab) {
+    if (tab === 'search') { setView('public'); setPublicScreen('search'); return; }
+    if (tab === 'scan')   { setView('public'); setPublicScreen('scan');   return; }
+    if (tab === 'saved')  {
+      if (currentUser) { setShowSaved(true); setView('public'); setPublicScreen('home'); }
+      else setShowLogin(true);
+      return;
+    }
+    if (tab === 'profile') {
+      if (currentUser) setView('profile');
+      else setShowLogin(true);
+      return;
+    }
+  }
+
   return (
     <div className="app">
+      <TopBar
+        currentUser={currentUser}
+        isAdmin={isAdmin}
+        authChecked={authChecked}
+        onShowSaved={() => setShowSaved(true)}
+        onLoginRequest={() => setShowLogin(true)}
+        onAdminClick={() => setView(view === 'admin' ? 'public' : 'admin')}
+      />
+
       <nav className="view-switcher" aria-label="Primary">
         <button
           className={view === 'public' ? 'active' : ''}
@@ -97,6 +136,12 @@ function App() {
 
       {activeView}
 
+      <BottomNav
+        activeTab={navActiveTab()}
+        onChange={handleNavChange}
+        isLoggedIn={Boolean(currentUser)}
+      />
+
       {showLogin && (
         <LoginModal
           onLogin={handleLogin}

frontend/src/components/BottomNav.css

@@ -0,0 +1,89 @@
+/* BottomNav — mobile-only fixed bottom tab bar. Desktop hides via display:none above 768px. */
+
+.bottom-nav {
+  display: none;
+}
+
+@media (max-width: 768px) {
+  .bottom-nav {
+    display: grid;
+    grid-template-columns: repeat(4, 1fr);
+    position: fixed;
+    left: 0;
+    right: 0;
+    bottom: 0;
+    z-index: 50;
+    padding: 0.4rem 0.5rem calc(0.4rem + env(safe-area-inset-bottom));
+    background: var(--glass-bg);
+    -webkit-backdrop-filter: saturate(180%) blur(20px);
+    backdrop-filter: saturate(180%) blur(20px);
+    border-top: 1px solid var(--border);
+  }
+
+  .bottom-nav-item {
+    display: flex;
+    flex-direction: column;
+    align-items: center;
+    justify-content: flex-end;
+    gap: 0.25rem;
+    padding: 0.25rem 0.25rem 0.1rem;
+    background: transparent;
+    border: none;
+    cursor: pointer;
+    color: var(--text-muted);
+    font: inherit;
+    -webkit-tap-highlight-color: transparent;
+    transition: color 0.15s;
+  }
+
+  .bottom-nav-item.disabled {
+    opacity: 0.5;
+    cursor: not-allowed;
+  }
+
+  .nav-icon-wrap {
+    display: inline-flex;
+    align-items: center;
+    justify-content: center;
+    width: 2.5rem;
+    height: 2.5rem;
+    border-radius: 999px;
+    color: inherit;
+    transition: background 0.2s, color 0.2s, transform 0.2s;
+  }
+
+  /* Elevated center tab (Scan) — sits above the bar like iOS center FAB */
+  .bottom-nav-item:nth-child(2) {
+    margin-top: -1.1rem;
+  }
+
+  .nav-icon-wrap--elevated {
+    background: var(--primary);
+    color: #fff;
+    width: 3.25rem;
+    height: 3.25rem;
+    box-shadow:
+      0 0 0 4px var(--glass-bg),
+      0 8px 18px rgba(15, 118, 110, 0.4),
+      0 2px 6px rgba(15, 118, 110, 0.25);
+  }
+
+  .bottom-nav-item.active .nav-label {
+    color: var(--primary);
+    font-weight: 700;
+  }
+
+  .bottom-nav-item.active .nav-icon-wrap:not(.nav-icon-wrap--elevated) {
+    color: var(--primary);
+  }
+
+  .bottom-nav-item:active .nav-icon-wrap--elevated {
+    transform: scale(0.94);
+  }
+
+  .nav-label {
+    font-size: 0.68rem;
+    line-height: 1;
+    letter-spacing: 0.01em;
+  }
+}

frontend/src/components/BottomNav.jsx

@@ -0,0 +1,44 @@
+import { IconSearch, IconScan, IconBell, IconUser } from './icons';
+import './BottomNav.css';
+
+// ponytail: 4 tabs. Scan is the 2nd item (center) and gets the elevated teal pill.
+// ponytail: when logged out, "saved" slot morphs into Login. Profile is disabled until login.
+function BottomNav({ activeTab, onChange, isLoggedIn }) {
+  const tabs = [
+    { id: 'search', label: 'Search', Icon: IconSearch },
+    { id: 'scan', label: 'Scan', Icon: IconScan, elevated: true },
+    { id: 'saved', label: 'Saved', Icon: IconBell, requiresAuth: true },
+    { id: 'profile', label: 'Profile', Icon: IconUser, requiresAuth: true },
+  ];
+
+  return (
+    <nav className="bottom-nav" aria-label="Primary">
+      {tabs.map(({ id, label, Icon, elevated, requiresAuth }) => {
+        const disabled = requiresAuth && !isLoggedIn;
+        const isActive = activeTab === id;
+        return (
+          <button
+            key={id}
+            type="button"
+            className={[
+              'bottom-nav-item',
+              isActive ? 'active' : '',
+              disabled ? 'disabled' : '',
+            ].filter(Boolean).join(' ')}
+            onClick={() => onChange(id)}
+            disabled={disabled}
+            aria-current={isActive ? 'page' : undefined}
+            aria-label={label}
+          >
+            <span className={`nav-icon-wrap${elevated ? ' nav-icon-wrap--elevated' : ''}`}>
+              <Icon size={elevated ? 24 : 22} />
+            </span>
+            <span className="nav-label">{label}</span>
+          </button>
+        );
+      })}
+    </nav>
+  );
+}
+
+export default BottomNav;

frontend/src/components/TopBar.css

@@ -0,0 +1,86 @@
+/* TopBar — mobile-only sticky header. Desktop hides via display:none above 768px. */
+
+.top-bar {
+  display: none;
+}
+
+@media (max-width: 768px) {
+  .top-bar {
+    display: flex;
+    align-items: center;
+    justify-content: space-between;
+    position: sticky;
+    top: 0;
+    z-index: 50;
+    padding: calc(0.65rem + env(safe-area-inset-top)) 1rem 0.65rem;
+    background: var(--glass-bg);
+    -webkit-backdrop-filter: saturate(180%) blur(20px);
+    backdrop-filter: saturate(180%) blur(20px);
+    border-bottom: 1px solid var(--border);
+  }
+
+  .topbar-brand {
+    display: inline-flex;
+    align-items: center;
+    gap: 0.5rem;
+    color: var(--text-main);
+  }
+
+  .topbar-brand-icon {
+    color: var(--primary);
+    flex-shrink: 0;
+  }
+
+  .topbar-brand-text {
+    font-size: 1.05rem;
+    font-weight: 800;
+    letter-spacing: -0.02em;
+  }
+
+  .topbar-actions {
+    display: inline-flex;
+    align-items: center;
+    gap: 0.4rem;
+    min-height: 2.25rem;
+  }
+
+  .topbar-action {
+    display: inline-flex;
+    align-items: center;
+    justify-content: center;
+    gap: 0.4rem;
+    min-height: 2.25rem;
+    padding: 0.45rem 0.7rem;
+    border: 1px solid transparent;
+    border-radius: 999px;
+    background: transparent;
+    color: var(--text-main);
+    cursor: pointer;
+    font-size: 0.85rem;
+    font-weight: 600;
+    transition: background 0.15s, color 0.15s, border-color 0.15s;
+  }
+
+  .topbar-action:hover {
+    background: var(--surface-muted);
+  }
+
+  .topbar-action--admin {
+    color: var(--primary);
+    border-color: rgba(15, 118, 110, 0.25);
+    background: rgba(15, 118, 110, 0.08);
+  }
+
+  .topbar-action--admin:hover {
+    background: rgba(15, 118, 110, 0.15);
+  }
+
+  .topbar-action--login {
+    color: var(--primary);
+    border-color: rgba(15, 118, 110, 0.25);
+  }
+
+  .topbar-action--placeholder {
+    width: 2.25rem;
+  }
+}

frontend/src/components/TopBar.jsx

@@ -0,0 +1,66 @@
+import { IconBell, IconCog, IconUser, IconLogo } from './icons';
+import './TopBar.css';
+
+function TopBar({
+  currentUser,
+  isAdmin,
+  onShowSaved,
+  onLoginRequest,
+  onAdminClick,
+  authChecked,
+}) {
+  // ponytail: action slot priority — admin pill > bell (logged-in) > login button (logged-out).
+  // ponytail: hidden on desktop via .top-bar { display: none } above 768px.
+  function renderAction() {
+    if (isAdmin) {
+      return (
+        <button
+          type="button"
+          className="topbar-action topbar-action--admin"
+          onClick={onAdminClick}
+          aria-label="Admin panel"
+        >
+          <IconCog size={18} />
+          <span>Admin</span>
+        </button>
+      );
+    }
+    if (currentUser) {
+      return (
+        <button
+          type="button"
+          className="topbar-action"
+          onClick={onShowSaved}
+          aria-label="Saved notifications"
+        >
+          <IconBell size={22} />
+        </button>
+      );
+    }
+    if (authChecked) {
+      return (
+        <button
+          type="button"
+          className="topbar-action topbar-action--login"
+          onClick={onLoginRequest}
+        >
+          <IconUser size={18} />
+          <span>Login</span>
+        </button>
+      );
+    }
+    return <span className="topbar-action topbar-action--placeholder" />;
+  }
+
+  return (
+    <header className="top-bar">
+      <div className="topbar-brand">
+        <IconLogo size={22} className="topbar-brand-icon" />
+        <span className="topbar-brand-text">FarmaFinder</span>
+      </div>
+      <div className="topbar-actions">{renderAction()}</div>
+    </header>
+  );
+}
+
+export default TopBar;

frontend/src/components/icons.jsx

@@ -0,0 +1,63 @@
+// ponytail: stroke-based line icons, 24x24, currentColor. Emojis stay for in-content use.
+// ponytail: add when a filled variant is needed for active states — swap stroke="currentColor" for fill.
+
+export function IconSearch({ size = 24, ...props }) {
+  return (
+    <svg width={size} height={size} viewBox="0 0 24 24" fill="none" stroke="currentColor"
+      strokeWidth="1.8" strokeLinecap="round" strokeLinejoin="round" aria-hidden="true" {...props}>
+      <circle cx="11" cy="11" r="7" />
+      <path d="m20 20-3.5-3.5" />
+    </svg>
+  );
+}
+
+export function IconScan({ size = 24, ...props }) {
+  return (
+    <svg width={size} height={size} viewBox="0 0 24 24" fill="none" stroke="currentColor"
+      strokeWidth="1.8" strokeLinecap="round" strokeLinejoin="round" aria-hidden="true" {...props}>
+      <path d="M3 7V5a2 2 0 0 1 2-2h2" />
+      <path d="M17 3h2a2 2 0 0 1 2 2v2" />
+      <path d="M21 17v2a2 2 0 0 1-2 2h-2" />
+      <path d="M7 21H5a2 2 0 0 1-2-2v-2" />
+      <path d="M7 8v8M11 8v8M15 8v8M19 8v8" />
+    </svg>
+  );
+}
+
+export function IconBell({ size = 24, ...props }) {
+  return (
+    <svg width={size} height={size} viewBox="0 0 24 24" fill="none" stroke="currentColor"
+      strokeWidth="1.8" strokeLinecap="round" strokeLinejoin="round" aria-hidden="true" {...props}>
+      <path d="M6 8a6 6 0 0 1 12 0c0 7 3 9 3 9H3s3-2 3-9" />
+      <path d="M10.3 21a1.94 1.94 0 0 0 3.4 0" />
+    </svg>
+  );
+}
+
+export function IconUser({ size = 24, ...props }) {
+  return (
+    <svg width={size} height={size} viewBox="0 0 24 24" fill="none" stroke="currentColor"
+      strokeWidth="1.8" strokeLinecap="round" strokeLinejoin="round" aria-hidden="true" {...props}>
+      <path d="M20 21v-2a4 4 0 0 0-4-4H8a4 4 0 0 0-4 4v2" />
+      <circle cx="12" cy="7" r="4" />
+    </svg>
+  );
+}
+
+export function IconCog({ size = 24, ...props }) {
+  return (
+    <svg width={size} height={size} viewBox="0 0 24 24" fill="none" stroke="currentColor"
+      strokeWidth="1.8" strokeLinecap="round" strokeLinejoin="round" aria-hidden="true" {...props}>
+      <circle cx="12" cy="12" r="3" />
+      <path d="M19.4 15a1.65 1.65 0 0 0 .33 1.82l.06.06a2 2 0 1 1-2.83 2.83l-.06-.06a1.65 1.65 0 0 0-1.82-.33 1.65 1.65 0 0 0-1 1.51V21a2 2 0 1 1-4 0v-.09a1.65 1.65 0 0 0-1-1.51 1.65 1.65 0 0 0-1.82.33l-.06.06a2 2 0 1 1-2.83-2.83l.06-.06a1.65 1.65 0 0 0 .33-1.82 1.65 1.65 0 0 0-1.51-1H3a2 2 0 1 1 0-4h.09a1.65 1.65 0 0 0 1.51-1 1.65 1.65 0 0 0-.33-1.82l-.06-.06a2 2 0 1 1 2.83-2.83l.06.06a1.65 1.65 0 0 0 1.82.33H9a1.65 1.65 0 0 0 1-1.51V3a2 2 0 1 1 4 0v.09a1.65 1.65 0 0 0 1 1.51 1.65 1.65 0 0 0 1.82-.33l.06-.06a2 2 0 1 1 2.83 2.83l-.06.06a1.65 1.65 0 0 0-.33 1.82V9a1.65 1.65 0 0 0 1.51 1H21a2 2 0 1 1 0 4h-.09a1.65 1.65 0 0 0-1.51 1z" />
+    </svg>
+  );
+}
+
+export function IconLogo({ size = 24, ...props }) {
+  return (
+    <svg width={size} height={size} viewBox="0 0 24 24" fill="currentColor" aria-hidden="true" {...props}>
+      <path d="M19 8h-1V6a3 3 0 0 0-3-3H9a3 3 0 0 0-3 3v2H5a3 3 0 0 0-3 3v6a3 3 0 0 0 3 3h14a3 3 0 0 0 3-3v-6a3 3 0 0 0-3-3zM8 6a1 1 0 0 1 1-1h6a1 1 0 0 1 1 1v2H8V6zm4 11a3 3 0 1 1 3-3 3 3 0 0 1-3 3z" />
+    </svg>
+  );
+}

frontend/src/views/PublicView.jsx

@@ -8,9 +8,15 @@ import HomeView from './HomeView';
 import ScannerView from './ScannerView';
 import { haversineKm, getUserPosition } from '../utils/geo';
 
-function PublicView({ currentUser, onLoginRequest }) {
-  // 'home' | 'scan' | 'search'
-  const [screen, setScreen] = useState('home');
+function PublicView({
+  currentUser,
+  onLoginRequest,
+  screen: screenProp,
+  onScreenChange,
+}) {
+  // ponytail: screen state lifted to App.jsx so BottomNav can switch directly.
+  const screen = screenProp ?? 'home';
+  const setScreen = onScreenChange ?? (() => {});
 
   const [searchQuery, setSearchQuery] = useState('');
   const [medicines, setMedicines] = useState([]);