feat(backend): migrate anonymous consents on login/register

apps/backend/server.js

@@ -1042,6 +1042,23 @@ app.put('/api/consents', async (req, res) => {
   }
 });
 
+// Migrate anonymous (session-based) consents to a user account on login/register
+async function migrateSessionConsents(userId, sessionId) {
+  if (!userId || !sessionId) return;
+  try {
+    const sessionConsents = await userDbAll('SELECT category, granted FROM user_consents WHERE session_id = ?', [sessionId]);
+    for (const consent of sessionConsents) {
+      await userDbRun(
+        `INSERT INTO user_consents (user_id, category, granted, updated_at) VALUES (?, ?, ?, CURRENT_TIMESTAMP) ON CONFLICT (user_id, category) DO UPDATE SET granted = ?, updated_at = CURRENT_TIMESTAMP`,
+        [userId, consent.category, consent.granted, consent.granted]
+      );
+    }
+    await userDbRun('DELETE FROM user_consents WHERE session_id = ?', [sessionId]);
+  } catch (error) {
+    console.error('Error migrating consents:', error);
+  }
+}
+
 // ========== RECENT SEARCHES (database-based) ==========
 
 const MAX_RECENT = 5;
@@ -1302,6 +1319,9 @@ app.post('/api/auth/login', loginLimiter, async (req, res) => {
     req.session.username = user.username;
     req.session.isAdmin = Boolean(user.is_admin);
 
+    // Migrate anonymous consents to user account
+    await migrateSessionConsents(user.id, req.sessionID);
+
     appMetrics.loginSuccessTotal.add(1);
     res.json({
       message: 'Login successful',
@@ -1352,6 +1372,9 @@ app.post('/api/auth/register', registerLimiter, async (req, res) => {
     req.session.username = u;
     req.session.isAdmin = false;
 
+    // Migrate anonymous consents to new user account
+    await migrateSessionConsents(result.lastID, req.sessionID);
+
     res.status(201).json({
       message: 'Registered',
       user: {