Enhance model and service documentation with detailed comments and descriptions

- Updated Group, Trip, User, and other model classes to include comprehensive documentation for better understanding and maintainability.
- Improved error handling and logging in services, including AuthService, ErrorService, and StorageService.
- Added validation and business logic explanations in ExpenseService and TripService.
- Refactored method comments to follow a consistent format across the codebase.
- Translated error messages and comments from French to English for consistency.

lib/blocs/auth/auth_bloc.dart

@@ -1,11 +1,38 @@
+/// Business Logic Component for managing authentication state.
+/// 
+/// The [AuthBloc] handles authentication-related events and manages the
+/// authentication state throughout the application. It coordinates with
+/// the [AuthRepository] to perform authentication operations and emits
+/// appropriate states based on the results.
+/// 
+/// Supported authentication methods:
+/// - Email and password authentication
+/// - Google Sign-In
+/// - Apple Sign-In
+/// - Password reset functionality
+/// 
+/// This bloc handles the following events:
+/// - [AuthCheckRequested]: Verifies current authentication status
+/// - [AuthSignInRequested]: Processes email/password sign-in
+/// - [AuthSignUpRequested]: Processes user registration
+/// - [AuthGoogleSignInRequested]: Processes Google authentication
+/// - [AuthAppleSignInRequested]: Processes Apple authentication
+/// - [AuthSignOutRequested]: Processes user sign-out
+/// - [AuthPasswordResetRequested]: Processes password reset requests
 import 'package:flutter_bloc/flutter_bloc.dart';
 import '../../repositories/auth_repository.dart';
 import 'auth_event.dart';
 import 'auth_state.dart';
 
+/// BLoC for managing authentication state and operations.
 class AuthBloc extends Bloc<AuthEvent, AuthState> {
+  /// Repository for authentication operations.
   final AuthRepository _authRepository;
 
+  /// Creates an [AuthBloc] with the provided [authRepository].
+  /// 
+  /// The bloc starts in the [AuthInitial] state and registers event handlers
+  /// for all supported authentication events.
   AuthBloc({required AuthRepository authRepository})
       : _authRepository = authRepository,
         super(AuthInitial()) {
@@ -18,6 +45,10 @@ class AuthBloc extends Bloc<AuthEvent, AuthState> {
     on<AuthPasswordResetRequested>(_onPasswordResetRequested);
   }
 
+  /// Handles [AuthCheckRequested] events.
+  /// 
+  /// Checks if a user is currently authenticated and emits the appropriate state.
+  /// If a user is found, attempts to fetch user data from Firestore.
   Future<void> _onAuthCheckRequested(
     AuthCheckRequested event,
     Emitter<AuthState> emit,
@@ -28,7 +59,7 @@ class AuthBloc extends Bloc<AuthEvent, AuthState> {
       final currentUser = _authRepository.currentUser;
       
       if (currentUser != null) {
-        // Récupérer les données utilisateur depuis Firestore
+        // Fetch user data from Firestore
         final user = await _authRepository.getUserFromFirestore(currentUser.uid);
         
         if (user != null) {
@@ -44,6 +75,10 @@ class AuthBloc extends Bloc<AuthEvent, AuthState> {
     }
   }
 
+  /// Handles [AuthSignInRequested] events.
+  /// 
+  /// Attempts to sign in a user with the provided email and password.
+  /// Emits [AuthAuthenticated] on success or [AuthError] on failure.
   Future<void> _onSignInRequested(
     AuthSignInRequested event,
     Emitter<AuthState> emit,
@@ -59,13 +94,17 @@ class AuthBloc extends Bloc<AuthEvent, AuthState> {
       if (user != null) {
         emit(AuthAuthenticated(user: user));
       } else {
-        emit(const AuthError(message: 'Email ou mot de passe incorrect'));
+        emit(const AuthError(message: 'Invalid email or password'));
       }
     } catch (e) {
       emit(AuthError(message: e.toString()));
     }
   }
 
+  /// Handles [AuthSignUpRequested] events.
+  /// 
+  /// Attempts to create a new user account with the provided information.
+  /// Emits [AuthAuthenticated] on success or [AuthError] on failure.
   Future<void> _onSignUpRequested(
     AuthSignUpRequested event,
     Emitter<AuthState> emit,
@@ -83,13 +122,17 @@ class AuthBloc extends Bloc<AuthEvent, AuthState> {
       if (user != null) {
         emit(AuthAuthenticated(user: user));
       } else {
-        emit(const AuthError(message: 'Erreur lors de l\'inscription'));
+        emit(const AuthError(message: 'Registration failed'));
       }
     } catch (e) {
       emit(AuthError(message: e.toString()));
     }
   }
 
+  /// Handles [AuthGoogleSignInRequested] events.
+  /// 
+  /// Attempts to sign in the user using Google authentication.
+  /// Emits [AuthAuthenticated] on success or [AuthError] on failure.
   Future<void> _onGoogleSignInRequested(
     AuthGoogleSignInRequested event,
     Emitter<AuthState> emit,
@@ -102,13 +145,17 @@ class AuthBloc extends Bloc<AuthEvent, AuthState> {
       if (user != null) {
         emit(AuthAuthenticated(user: user));
       } else {
-        emit(const AuthError(message: 'Connexion Google annulée'));
+        emit(const AuthError(message: 'Google sign-in cancelled'));
       }
     } catch (e) {
       emit(AuthError(message: e.toString()));
     }
   }
 
+  /// Handles [AuthAppleSignInRequested] events.
+  /// 
+  /// Attempts to sign in the user using Apple authentication.
+  /// Emits [AuthAuthenticated] on success or [AuthError] on failure.
   Future<void> _onAppleSignInRequested(
     AuthAppleSignInRequested event,
     Emitter<AuthState> emit,
@@ -121,13 +168,16 @@ class AuthBloc extends Bloc<AuthEvent, AuthState> {
       if (user != null) {
         emit(AuthAuthenticated(user: user));
       } else {
-        emit(const AuthError(message: 'Connexion Apple annulée'));
+        emit(const AuthError(message: 'Apple sign-in cancelled'));
       }
     } catch (e) {
       emit(AuthError(message: e.toString()));
     }
   }
 
+  /// Handles [AuthSignOutRequested] events.
+  /// 
+  /// Signs out the current user and emits [AuthUnauthenticated].
   Future<void> _onSignOutRequested(
     AuthSignOutRequested event,
     Emitter<AuthState> emit,
@@ -136,6 +186,10 @@ class AuthBloc extends Bloc<AuthEvent, AuthState> {
     emit(AuthUnauthenticated());
   }
 
+  /// Handles [AuthPasswordResetRequested] events.
+  /// 
+  /// Sends a password reset email to the specified email address.
+  /// Emits [AuthPasswordResetSent] on success or [AuthError] on failure.
   Future<void> _onPasswordResetRequested(
     AuthPasswordResetRequested event,
     Emitter<AuthState> emit,