Refactor user and theme management to use BLoC pattern; remove provider classes and integrate new services for user and group functionalities

lib/blocs/user/user_event.dart

@@ -0,0 +1,22 @@
+abstract class UserEvent {}
+
+class UserInitialized extends UserEvent {}
+
+class UserLoaded extends UserEvent {
+  final String userId;
+  
+  UserLoaded(this.userId);
+}
+
+class UserUpdated extends UserEvent {
+  final Map<String, dynamic> userData;
+  
+  UserUpdated(this.userData);
+}
+
+class UserLoggedOut extends UserEvent {}
+class LoadUser extends UserEvent {
+  final String userId;
+  
+  LoadUser(this.userId);
+}