Refactor signup page to use BLoC pattern and implement authentication repository

- Updated signup.dart to replace Provider with BLoC for state management.
- Created AuthRepository to handle authentication logic and Firestore user management.
- Added TripRepository and UserRepository for trip and user data management.
- Implemented methods for user sign-in, sign-up, and data retrieval in repositories.
- Enhanced trip management with create, update, delete, and participant management functionalities.
- Updated AuthService to include new methods for sign-in and sign-up.
- Removed unnecessary print statements from TripService for cleaner code.
- Added dependencies for flutter_bloc and equatable in pubspec.yaml.

Not tested yet

lib/blocs/trip/trip_event.dart

@@ -0,0 +1,71 @@
+import 'package:equatable/equatable.dart';
+import '../../data/models/trip.dart';
+
+abstract class TripEvent extends Equatable {
+  const TripEvent();
+
+  @override
+  List<Object?> get props => [];
+}
+
+class TripLoadRequested extends TripEvent {
+  final String userId;
+
+  const TripLoadRequested({required this.userId});
+
+  @override
+  List<Object?> get props => [userId];
+}
+
+class TripCreateRequested extends TripEvent {
+  final Trip trip;
+
+  const TripCreateRequested({required this.trip});
+
+  @override
+  List<Object?> get props => [trip];
+}
+
+class TripUpdateRequested extends TripEvent {
+  final Trip trip;
+
+  const TripUpdateRequested({required this.trip});
+
+  @override
+  List<Object?> get props => [trip];
+}
+
+class TripDeleteRequested extends TripEvent {
+  final String tripId;
+
+  const TripDeleteRequested({required this.tripId});
+
+  @override
+  List<Object?> get props => [tripId];
+}
+
+class TripParticipantAddRequested extends TripEvent {
+  final String tripId;
+  final String participantEmail;
+
+  const TripParticipantAddRequested({
+    required this.tripId,
+    required this.participantEmail,
+  });
+
+  @override
+  List<Object?> get props => [tripId, participantEmail];
+}
+
+class TripParticipantRemoveRequested extends TripEvent {
+  final String tripId;
+  final String participantEmail;
+
+  const TripParticipantRemoveRequested({
+    required this.tripId,
+    required this.participantEmail,
+  });
+
+  @override
+  List<Object?> get props => [tripId, participantEmail];
+}