feat: add Expo Push notifications for mobile and configure EXPO_ACCESS_TOKEN

- Backend: add expo_push_tokens table, expo-register/unregister endpoints, hybrid VAPID+Expo push sender
- Mobile: register Expo push token on app launch, bell toggle on medicine/pharmacy detail screens
- .env.example: document EXPO_ACCESS_TOKEN configuration
- Dark mode hover fixes for search suggestions and recent buttons

apps/frontend/src/views/SearchView.css

@@ -57,12 +57,20 @@
   font-weight: 700;
 }
 
+[data-theme="dark"] .suggestion-btn:hover {
+  background: #07243d;
+}
+
 .suggestion-btn--neutral-1 {
   background: var(--suggestion-1);
   color: var(--suggestion-text);
   border: 1px solid var(--suggestion-border-1);
 }
 
+[data-theme="dark"] .suggestion-btn--neutral-1:hover {
+  background: #1e2225;
+}
+
 .suggestion-btn--neutral-2 {
   background: var(--suggestion-2);
   color: var(--suggestion-text);
@@ -179,6 +187,10 @@
   transition: opacity 0.15s;
 }
 
+[data-theme="dark"] .recent-btn {
+  background: #053d13;
+}
+
 .recent-btn:active {
   opacity: 0.85;
 }