feat(web): add consent sync utility

apps/frontend/src/utils/consent.js

@@ -0,0 +1,75 @@
+const CONSENT_KEY = 'farmafinder_consents';
+
+const DEFAULT_CONSENTS = {
+  essential: true,
+  analytics: false,
+  preferences: false,
+  health_data: false,
+};
+
+export function getLocalConsents() {
+  try {
+    const stored = localStorage.getItem(CONSENT_KEY);
+    if (stored) {
+      const parsed = JSON.parse(stored);
+      return { ...DEFAULT_CONSENTS, ...parsed, essential: true };
+    }
+  } catch {}
+  return { ...DEFAULT_CONSENTS };
+}
+
+export function setLocalConsents(consents) {
+  try {
+    localStorage.setItem(CONSENT_KEY, JSON.stringify(consents));
+  } catch {}
+}
+
+export function hasConsentChoice() {
+  try {
+    return localStorage.getItem(CONSENT_KEY) !== null;
+  } catch {
+    return false;
+  }
+}
+
+export async function fetchServerConsents() {
+  try {
+    const res = await fetch('/api/consents', { credentials: 'include' });
+    if (res.ok) {
+      const serverConsents = await res.json();
+      setLocalConsents(serverConsents);
+      return serverConsents;
+    }
+  } catch {}
+  return null;
+}
+
+export async function saveConsents(consents) {
+  const toSave = { ...consents, essential: true };
+  setLocalConsents(toSave);
+  try {
+    const res = await fetch('/api/consents', {
+      method: 'PUT',
+      headers: { 'Content-Type': 'application/json' },
+      credentials: 'include',
+      body: JSON.stringify({
+        categories: {
+          analytics: toSave.analytics,
+          preferences: toSave.preferences,
+          health_data: toSave.health_data,
+        },
+      }),
+    });
+    if (res.ok) {
+      const serverConsents = await res.json();
+      setLocalConsents(serverConsents);
+      return serverConsents;
+    }
+  } catch {}
+  return toSave;
+}
+
+export function hasConsent(category) {
+  const consents = getLocalConsents();
+  return consents[category] === true;
+}