fix(auth): prevent AuthNotifier auto-dispose causing theme toggle logout

Applied @persistentRiverpod annotation to AuthNotifier so it persists
for app lifetime. Previously, theme changes could trigger AuthProvider
rebuild via auto-dispose, causing AsyncLoading state and auth issues.

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

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

docs/ARCHITECTURE.md

@@ -447,13 +447,13 @@ Dio coreApiClient(Ref ref) { ... }
 
 **When to use `@persistentRiverpod`:**
 
-| Use Case | Annotation |
-|----------|------------|
-| API clients with interceptors | `@persistentRiverpod` |
-| Theme/config providers | `@persistentRiverpod` |
-| Auth state provider | `@persistentRiverpod` |
-| Feature data providers | `@riverpod` (default) |
-| UI state providers | `@riverpod` (default) |
+| Use Case | Annotation | Example |
+|----------|------------|---------|
+| API clients with interceptors | `@persistentRiverpod` | `coreApiClient`, `tatlockApiClient` |
+| Auth state provider | `@persistentRiverpod` | `AuthNotifier` |
+| Theme/config providers | `@persistentRiverpod` | `ThemeNotifier` |
+| Feature data providers | `@riverpod` (default) | `ContainersNotifier` |
+| UI state providers | `@riverpod` (default) | `SearchFilterNotifier` |
 
 ## File Naming Conventions