feat: Enhance trip management features and improve UI responsiveness

- Implemented AutomaticKeepAliveClientMixin in HomeContent to maintain state during navigation.
- Modified trip loading logic to trigger after the first frame for better performance.
- Updated trip loading events to use LoadTripsByUserId for consistency.
- Added temporary success messages for trip creation and operations.
- Improved UI elements for better user experience, including updated text styles and spacing.
- Refactored trip model to support Firestore timestamps and improved error handling during parsing.
- Streamlined trip repository methods for better clarity and performance.
- Enhanced trip service methods to ensure correct mapping from Firestore documents.
- Removed unnecessary trip reset logic on logout.

lib/blocs/trip/trip_state.dart

@@ -15,16 +15,30 @@ class TripLoading extends TripState {}
 class TripLoaded extends TripState {
   final List<Trip> trips;
 
-  const TripLoaded({required this.trips});
+  const TripLoaded(this.trips);
 
   @override
   List<Object?> get props => [trips];
 }
 
+// NOUVEAU : État pour indiquer qu'un voyage a été créé avec succès
+class TripCreated extends TripState {
+  final String tripId;
+  final String message;
+
+  const TripCreated({
+    required this.tripId,
+    this.message = 'Voyage créé avec succès',
+  });
+
+  @override
+  List<Object?> get props => [tripId, message];
+}
+
 class TripOperationSuccess extends TripState {
   final String message;
 
-  const TripOperationSuccess({required this.message});
+  const TripOperationSuccess(this.message);
 
   @override
   List<Object?> get props => [message];
@@ -33,7 +47,7 @@ class TripOperationSuccess extends TripState {
 class TripError extends TripState {
   final String message;
 
-  const TripError({required this.message});
+  const TripError(this.message);
 
   @override
   List<Object?> get props => [message];