refactor: optimize providers with keepAlive for improved state management

- Updated multiple providers to use `@Riverpod(keepAlive: true)` for better state retention throughout the app lifecycle.
- Enhanced `SocketConnectionStream` and `ConversationDeltaStream` with comments clarifying the purpose of public getters.
- Improved error handling in the `_ChatPageState` by ensuring proper checks for mounted state before using context.
- Added comments to clarify the rationale behind keepAlive usage in various providers, ensuring better maintainability and understanding of the codebase.

lib/features/auth/providers/unified_auth_providers.dart

@@ -60,6 +60,8 @@ final hasSavedCredentialsProvider2 = FutureProvider<bool>((ref) async {
 
 /// Computed providers for UI consumption
 /// These automatically update when auth state changes
+/// These are keepAlive since they derive from keepAlive authStateManagerProvider
+/// and are used throughout the app lifecycle
 
 final isAuthenticatedProvider2 = Provider<bool>((ref) {
   final authState = ref.watch(authStateManagerProvider);