feat(auth): extract user info from JWT, skip core-api sync

- Decode JWT claims (name, email, groups) directly in Flutter
- No longer calls /auth/sync endpoint (avoids CORS preflight issues)
- Bearer token used for subsequent API authentication

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

lib/core/auth/auth_provider.dart

@@ -1,4 +1,4 @@
-import 'dart:convert';
+import 'dart:convert' show base64Url, jsonDecode, jsonEncode, utf8;
 import 'dart:developer' as developer;
 
 import 'package:flutter/foundation.dart' show kIsWeb;
@@ -265,23 +265,27 @@ class AuthNotifier extends _$AuthNotifier {
       final oidcService = OidcServiceWeb();
       final tokens = await oidcService.exchangeCode(code, callbackState);
 
-      // Step 2: Sync with core-api to get user profile and roles
-      developer.log('Syncing with core-api', name: 'auth');
-      final authDatasource = ref.read(authDatasourceProvider);
-      final syncResponse = await authDatasource.syncUser(tokens.accessToken);
+      // Step 2: Decode JWT to extract user info (skip core-api sync)
+      final claims = _decodeJwtClaims(tokens.accessToken);
+      final userName = claims['name'] as String? ??
+          claims['preferred_username'] as String? ??
+          'User';
+      final userEmail = claims['email'] as String? ?? '';
+      final authentikId = claims['sub'] as String?;
+      final groups = (claims['groups'] as List<dynamic>?)?.cast<String>() ?? [];
 
-      // Step 3: Store credentials and user data
+      developer.log('JWT claims: name=$userName, email=$userEmail, groups=$groups', name: 'auth');
+
+      // Step 3: Store credentials and user data from JWT
       await _storeAuth(
         accessToken: tokens.accessToken,
         refreshToken: tokens.refreshToken,
         expiresAt: tokens.expiresAt,
-        userId: syncResponse.userId,
-        authentikId: syncResponse.authentikId,
-        userName: syncResponse.name,
-        userEmail: syncResponse.email,
-        avatarUrl: syncResponse.avatarUrl,
-        roles: syncResponse.roles,
-        preferences: syncResponse.preferences,
+        authentikId: authentikId,
+        userName: userName,
+        userEmail: userEmail,
+        // Roles from groups - for now just store group names
+        // Full role parsing can be done later if needed
       );
 
       state = AsyncData(AuthState(
@@ -289,19 +293,12 @@ class AuthNotifier extends _$AuthNotifier {
         accessToken: tokens.accessToken,
         refreshToken: tokens.refreshToken,
         expiresAt: tokens.expiresAt,
-        userId: syncResponse.userId,
-        authentikId: syncResponse.authentikId,
-        userName: syncResponse.name,
-        userEmail: syncResponse.email,
-        avatarUrl: syncResponse.avatarUrl,
-        roles: syncResponse.roles,
-        preferences: syncResponse.preferences,
+        authentikId: authentikId,
+        userName: userName,
+        userEmail: userEmail,
       ));
 
-      developer.log(
-        'Authenticated as ${syncResponse.name} with ${syncResponse.roles.length} roles',
-        name: 'auth',
-      );
+      developer.log('Authenticated as $userName', name: 'auth');
 
       // Clean up the URL by removing the query parameters
       web_utils.replaceUrl('/');
@@ -314,6 +311,35 @@ class AuthNotifier extends _$AuthNotifier {
     }
   }
 
+  /// Decode JWT payload without verification (validation happens server-side).
+  Map<String, dynamic> _decodeJwtClaims(String jwt) {
+    try {
+      final parts = jwt.split('.');
+      if (parts.length != 3) {
+        developer.log('Invalid JWT format', name: 'auth');
+        return {};
+      }
+
+      // Decode the payload (second part)
+      String payload = parts[1];
+      // Add padding if needed for base64
+      switch (payload.length % 4) {
+        case 2:
+          payload += '==';
+          break;
+        case 3:
+          payload += '=';
+          break;
+      }
+
+      final decoded = utf8.decode(base64Url.decode(payload));
+      return jsonDecode(decoded) as Map<String, dynamic>;
+    } catch (e) {
+      developer.log('Failed to decode JWT: $e', name: 'auth');
+      return {};
+    }
+  }
+
   /// Sign out and clear stored credentials.
   Future<void> signOut() async {
     await _clearStoredAuth();