feat: add user search functionality

- Implemented `GET /users/search` endpoint in the backend to enable user search by username or display name.
- Added `search` method in `UsersService` and `UsersRepository`.
- Updated frontend `UserService` to support the new search API.

backend/src/users/users.service.ts

@@ -106,6 +106,16 @@ export class UsersService {
 		};
 	}
 
+	async search(query: string) {
+		const users = await this.usersRepository.search(query);
+		return users.map((user) => ({
+			...user,
+			avatarUrl: user.avatarUrl
+				? this.s3Service.getPublicUrl(user.avatarUrl)
+				: null,
+		}));
+	}
+
 	async findOne(uuid: string) {
 		const user = await this.usersRepository.findOne(uuid);
 		if (!user) return null;