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

pubspec.lock

@@ -25,6 +25,14 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "1.1.3"
+  bloc:
+    dependency: transitive
+    description:
+      name: bloc
+      sha256: "106842ad6569f0b60297619e9e0b1885c2fb9bf84812935490e6c5275777804e"
+      url: "https://pub.dev"
+    source: hosted
+    version: "8.1.4"
   boolean_selector:
     dependency: transitive
     description:
@@ -97,6 +105,14 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "1.0.8"
+  equatable:
+    dependency: "direct main"
+    description:
+      name: equatable
+      sha256: "567c64b3cb4cf82397aac55f4f0cbd3ca20d77c6c03bedbc4ceaddc08904aef7"
+      url: "https://pub.dev"
+    source: hosted
+    version: "2.0.7"
   fake_async:
     dependency: transitive
     description:
@@ -174,6 +190,14 @@ packages:
     description: flutter
     source: sdk
     version: "0.0.0"
+  flutter_bloc:
+    dependency: "direct main"
+    description:
+      name: flutter_bloc
+      sha256: b594505eac31a0518bdcb4b5b79573b8d9117b193cc80cc12e17d639b10aa27a
+      url: "https://pub.dev"
+    source: hosted
+    version: "8.1.6"
   flutter_lints:
     dependency: "direct dev"
     description: