feat: silent OIDC auth with JWT Bearer tokens for web

- Add prompt=none to silently obtain JWT when Authentik session exists
- Flutter sends Bearer token to core-api instead of forward auth cookies
- Fixes cross-subdomain cookie issues between home/api.schweitz.net
- Callback syncs with /auth/sync for user profile and roles
- API interceptor now adds Bearer token on web

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

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

lib/core/auth/oidc_service_web.dart

@@ -34,7 +34,12 @@ class OidcServiceWeb implements OidcService {
   ///
   /// Returns a URL that the browser should navigate to for authentication.
   /// The [codeVerifier] and [state] are stored for later verification.
-  Future<String> getAuthorizationUrl() async {
+  ///
+  /// If [silent] is true, adds `prompt=none` to skip login UI.
+  /// This is used when the user already has an Authentik session (via NPM).
+  /// Authentik will instantly redirect back with a code, or return an error
+  /// if there's no valid session.
+  Future<String> getAuthorizationUrl({bool silent = false}) async {
     // Fetch OIDC discovery document
     final discovery = await _fetchDiscovery();
     final authEndpoint = discovery['authorization_endpoint'] as String;
@@ -59,10 +64,11 @@ class OidcServiceWeb implements OidcService {
       'code_challenge': codeChallenge,
       'code_challenge_method': 'S256',
       'state': state,
+      if (silent) 'prompt': 'none', // Silent auth - no UI, instant redirect
     };
 
     final uri = Uri.parse(authEndpoint).replace(queryParameters: params);
-    developer.log('Authorization URL: $uri', name: 'oidc_web');
+    developer.log('Authorization URL (silent=$silent): $uri', name: 'oidc_web');
     return uri.toString();
   }