fix: make Continue as Guest button visible, guard wishlist for guests

The guest button was nearly invisible (grey text, fontSize 13 on dark
background). Now uses white70, fontSize 15, TextButton with proper
tap padding. Also guards wishlist toggle on event detail page.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

lib/screens/learn_more_screen.dart

@@ -10,6 +10,7 @@ import 'package:cached_network_image/cached_network_image.dart';
 
 import '../features/events/models/event_models.dart';
 import '../features/events/services/events_service.dart';
+import '../core/auth/auth_guard.dart';
 
 class LearnMoreScreen extends StatefulWidget {
   final int eventId;
@@ -345,7 +346,10 @@ class _LearnMoreScreenState extends State<LearnMoreScreen> {
                   _squareIconButton(
                     icon: _wishlisted ? Icons.favorite : Icons.favorite_border,
                     iconColor: _wishlisted ? Colors.redAccent : Colors.white,
-                    onTap: () => setState(() => _wishlisted = !_wishlisted),
+                    onTap: () {
+                      if (!AuthGuard.requireLogin(context, reason: 'Sign in to save events to your wishlist.')) return;
+                      setState(() => _wishlisted = !_wishlisted);
+                    },
                   ),
                 ],
               ),

lib/screens/login_screen.dart

@@ -515,21 +515,25 @@ class _LoginScreenState extends State<LoginScreen> {
 
                         // Continue as Guest
                         Center(
-                          child: GestureDetector(
+                          child: TextButton(
-                            onTap: () {
+                            onPressed: () {
                               AuthGuard.setGuest(true);
                               Navigator.of(context).pushAndRemoveUntil(
                                 MaterialPageRoute(builder: (_) => const HomeScreen()),
                                 (route) => false,
                               );
                             },
+                            style: TextButton.styleFrom(
+                              padding: const EdgeInsets.symmetric(horizontal: 24, vertical: 12),
+                            ),
                             child: const Text(
                               'Continue as Guest',
                               style: TextStyle(
-                                color: _textMuted,
+                                color: Colors.white70,
-                                fontSize: 13,
+                                fontSize: 15,
+                                fontWeight: FontWeight.w500,
                                 decoration: TextDecoration.underline,
-                                decorationColor: _textMuted,
+                                decorationColor: Colors.white70,
                               ),
                             ),
                           ),