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_event.dart

@@ -1,18 +1,37 @@
 import 'package:equatable/equatable.dart';
 
+/// Abstract base class for all authentication-related events.
+/// 
+/// This class extends [Equatable] to enable value equality for event comparison.
+/// All authentication events in the application should inherit from this class.
 abstract class AuthEvent extends Equatable {
+  /// Creates a new [AuthEvent].
   const AuthEvent();
 
   @override
   List<Object?> get props => [];
 }
 
+/// Event to check the current authentication status.
+/// 
+/// This event is typically dispatched when the app starts to determine
+/// if a user is already authenticated.
 class AuthCheckRequested extends AuthEvent {}
 
+/// Event to request user sign-in with email and password.
+/// 
+/// This event contains the user's credentials and triggers the authentication
+/// process when dispatched to the [AuthBloc].
 class AuthSignInRequested extends AuthEvent {
+  /// The user's email address.
   final String email;
+  
+  /// The user's password.
   final String password;
 
+  /// Creates a new [AuthSignInRequested] event.
+  /// 
+  /// Both [email] and [password] are required parameters.
   const AuthSignInRequested({
     required this.email,
     required this.password,
@@ -22,12 +41,26 @@ class AuthSignInRequested extends AuthEvent {
   List<Object?> get props => [email, password];
 }
 
+/// Event to request user registration with email, password, and personal information.
+/// 
+/// This event contains all necessary information to create a new user account
+/// and triggers the registration process when dispatched to the [AuthBloc].
 class AuthSignUpRequested extends AuthEvent {
+  /// The user's email address.
   final String email;
+  
+  /// The user's password.
   final String password;
+  
+  /// The user's last name.
   final String nom;
+  
+  /// The user's first name.
   final String prenom;
 
+  /// Creates a new [AuthSignUpRequested] event.
+  /// 
+  /// All parameters are required for user registration.
   const AuthSignUpRequested({
     required this.email,
     required this.password,
@@ -39,15 +72,33 @@ class AuthSignUpRequested extends AuthEvent {
   List<Object?> get props => [email, password, nom, prenom];
 }
 
+/// Event to request user sign-in using Google authentication.
+/// 
+/// This event triggers the Google sign-in flow when dispatched to the [AuthBloc].
 class AuthGoogleSignInRequested extends AuthEvent {}
 
+/// Event to request user sign-in using Apple authentication.
+/// 
+/// This event triggers the Apple sign-in flow when dispatched to the [AuthBloc].
 class AuthAppleSignInRequested extends AuthEvent {}
 
+/// Event to request user sign-out.
+/// 
+/// This event triggers the sign-out process and clears the user session
+/// when dispatched to the [AuthBloc].
 class AuthSignOutRequested extends AuthEvent {}
 
+/// Event to request a password reset for a user account.
+/// 
+/// This event triggers the password reset process by sending a reset email
+/// to the specified email address.
 class AuthPasswordResetRequested extends AuthEvent {
+  /// The email address to send the password reset link to.
   final String email;
 
+  /// Creates a new [AuthPasswordResetRequested] event.
+  /// 
+  /// The [email] parameter is required.
   const AuthPasswordResetRequested({required this.email});
 
   @override