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/repositories/users.repository.ts

@@ -1,5 +1,5 @@
 import { Injectable } from "@nestjs/common";
-import { and, eq, lte, sql } from "drizzle-orm";
+import { and, count, eq, ilike, or, sql } from "drizzle-orm";
 import { DatabaseService } from "../../database/database.service";
 import { contents, favorites, users } from "../../database/schemas";
 
@@ -97,6 +97,21 @@ export class UsersRepository {
 		return result[0] || null;
 	}
 
+	async search(query: string) {
+		return this.databaseService.db
+			.select({
+				uuid: users.uuid,
+				username: users.username,
+				displayName: users.displayName,
+				avatarUrl: users.avatarUrl,
+			})
+			.from(users)
+			.where(
+				or(ilike(users.username, `%${query}%`), ilike(users.displayName, `%${query}%`)),
+			)
+			.limit(10);
+	}
+
 	async findOne(uuid: string) {
 		const result = await this.databaseService.db
 			.select()