fix: use PetMood enum in _petMessage, remove dead Routes.home

- _petMessage now accepts PetMood enum directly (was String) — exhaustive
  switch, no silent fall-through on rename
- Remove unused Routes.home = '/' constant (initialLocation uses Routes.tasks)

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

lib/core/router/routes.dart

@@ -1,6 +1,5 @@
 /// Route name constants for go_router navigation.
 abstract final class Routes {
-  static const home = '/';
   static const tasks = '/tasks';
   static const pet = '/pet';
   static const zen = '/zen';

lib/features/tasks/screens/tasks_screen.dart

@@ -72,7 +72,7 @@ class TasksScreen extends ConsumerWidget {
                       petType: userState.petType,
                       petName: userState.petName,
                       mood: petMood.emoji,
-                      message: _petMessage(petMood.name, userState.petName),
+                      message: _petMessage(petMood, userState.petName),
                     ),
                     const SizedBox(height: 16),
 
@@ -154,12 +154,11 @@ class TasksScreen extends ConsumerWidget {
     );
   }
 
-  static String _petMessage(String mood, String petName) {
+  static String _petMessage(PetMood mood, String petName) {
     return switch (mood) {
-      'happy' => '$petName je šťastná! Jde ti to skvěle \u{1F44F}',
-      'neutral' => '$petName tě čeká! Co dnes zvládneme? \u{2728}',
-      'sad' => '$petName tě podporuje. Zkus jeden úkol \u{1F495}',
-      _ => '$petName je tady pro tebe \u{1F60A}',
+      PetMood.happy => '$petName je šťastná! Jde ti to skvěle \u{1F44F}',
+      PetMood.neutral => '$petName tě čeká! Co dnes zvládneme? \u{2728}',
+      PetMood.sad => '$petName tě podporuje. Zkus jeden úkol \u{1F495}',
     };
   }
 }