feat: Add initial backend server with user authentication, session management, and playlist CRUD functionality.

lib/features/auth/providers/auth_provider.dart

@@ -1,5 +1,5 @@
 import 'package:flutter_riverpod/flutter_riverpod.dart';
-import '../../../core/database/hive_service.dart';
+import '../../../core/services/auth_api_service.dart';
 import '../../../core/models/app_user.dart';
 
 /// Auth state
@@ -7,11 +7,13 @@ class AuthState {
   final AppUser? currentUser;
   final bool isLoading;
   final String? errorMessage;
+  final bool isInitialized;
 
   const AuthState({
     this.currentUser,
     this.isLoading = false,
     this.errorMessage,
+    this.isInitialized = false,
   });
 
   bool get isAuthenticated => currentUser != null;
@@ -21,52 +23,83 @@ class AuthState {
     AppUser? currentUser,
     bool? isLoading,
     String? errorMessage,
+    bool? isInitialized,
+    bool clearUser = false,
   }) {
     return AuthState(
-      currentUser: currentUser ?? this.currentUser,
+      currentUser: clearUser ? null : (currentUser ?? this.currentUser),
       isLoading: isLoading ?? this.isLoading,
       errorMessage: errorMessage,
+      isInitialized: isInitialized ?? this.isInitialized,
     );
   }
 }
 
-/// Auth notifier
+/// Auth notifier using API
 class AuthNotifier extends StateNotifier<AuthState> {
-  AuthNotifier() : super(const AuthState());
+  final AuthApiService _authService = AuthApiService();
+
+  AuthNotifier() : super(const AuthState()) {
+    // Auto-check for existing session
+    checkSession();
+  }
+
+  /// Check if there's an existing valid session
+  Future<void> checkSession() async {
+    state = state.copyWith(isLoading: true);
+    
+    try {
+      final user = await _authService.getCurrentUser();
+      if (user != null) {
+        state = AuthState(
+          currentUser: user,
+          isLoading: false,
+          isInitialized: true,
+        );
+      } else {
+        state = const AuthState(isInitialized: true);
+      }
+    } catch (e) {
+      state = const AuthState(isInitialized: true);
+    }
+  }
 
   /// Login with username and password
   Future<bool> login(String username, String password) async {
     state = state.copyWith(isLoading: true, errorMessage: null);
 
     try {
-      final usersBox = HiveService.usersBox;
+      final result = await _authService.login(username, password);
 
-      // Search for user by username
-      final user = usersBox.values.firstWhere(
-        (user) => user.username == username,
-        orElse: () => throw Exception('User not found'),
-      );
-
-      // Verify password using salt-based hashing
-      if (!HiveService.verifyPassword(password, user.passwordHash)) {
-        throw Exception('Invalid password');
+      if (result.success && result.user != null) {
+        state = AuthState(
+          currentUser: result.user,
+          isLoading: false,
+          isInitialized: true,
+        );
+        return true;
+      } else {
+        state = AuthState(
+          isLoading: false,
+          isInitialized: true,
+          errorMessage: result.error ?? 'Login failed',
+        );
+        return false;
       }
-
-      state = AuthState(currentUser: user, isLoading: false);
-      return true;
     } catch (e) {
       state = AuthState(
         isLoading: false,
-        errorMessage: 'Invalid username or password',
+        isInitialized: true,
+        errorMessage: 'Network error: $e',
       );
       return false;
     }
   }
 
-
   /// Logout current user
-  void logout() {
-    state = const AuthState();
+  Future<void> logout() async {
+    await _authService.logout();
+    state = const AuthState(isInitialized: true);
   }
 
   /// Get current user