implement auth login and register with MongoDB

- Add AuthController login/register endpoints with error handling
- Implement AuthService with password validation and user creation
- Add MongoUserRepository with findByEmail and create methods
- Implement password hashing with bcrypt
- Add dotenv for environment variable support
- Add Docker Compose setup for MongoDB + Mongo Express
- Stub AuthMiddleware with fake user for testing
- Update CLAUDE.md with implementation status

apps/server/src/repositories/mongo/MongoUserRepository.ts

@@ -8,10 +8,12 @@ export class MongoUserRepository implements UserRepository {
   }
 
   async findByEmail(email: string): Promise<User | null> {
-    throw new Error('Not implemented');
+    const user = await UserModel.findOne({ email: email.toLowerCase() });
+    return user ? user.toJSON() as User : null;
   }
 
   async create(data: CreateUserData): Promise<User> {
-    throw new Error('Not implemented');
+    const user = await UserModel.create(data);
+    return user.toJSON() as User;
   }
 }