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/account/account_state.dart

@@ -1,3 +1,38 @@
+/// The abstract base class for all account-related states used by the AccountBloc.
+///
+/// Extends Equatable to enable value-based comparisons between state
+/// instances. Subclasses should provide the relevant properties by
+/// overriding `props` so that the bloc can correctly determine whether
+/// the state has changed.
+ 
+/// Represents the initial state of the account feature.
+///
+/// Used before any account-related action has started or when the bloc
+/// has been freshly created.
+ 
+/// Indicates that an account-related operation is currently in progress.
+///
+/// This state is typically emitted while fetching account data, creating,
+/// updating, or deleting an account so the UI can show a loading indicator.
+ 
+/// Emitted when a collection of accounts has been successfully loaded.
+///
+/// Contains:
+/// - `accounts`: the list of Account models retrieved from the repository.
+///
+/// Use this state to display fetched account data in the UI.
+ 
+/// Represents a successful account operation that does not necessarily
+/// carry account data (e.g., after creating, updating, or deleting an account).
+///
+/// Contains:
+/// - `message`: a human-readable success message that can be shown to the user.
+ 
+/// Represents an error that occurred during an account-related operation.
+///
+/// Contains:
+/// - `message`: a human-readable error description suitable for logging
+///   or displaying to the user.
 import 'package:equatable/equatable.dart';
 import '../../models/account.dart';