feat(auth): add optional authentication guard and extend AuthModule providers

Introduce `OptionalAuthGuard` to allow conditional authentication for routes. Update `AuthModule` to include `AuthGuard`, `OptionalAuthGuard`, and `RolesGuard` in providers and exports for broader reuse.

feat(app): integrate `AdminModule` into app module

Add `AdminModule` to the app's main module to enable administration functionalities.

feat(users): enhance user profiles with bio and avatar fields

Extend `UpdateUserDto` to include optional `bio` and `avatarUrl` fields for better user customization.

feat(categories): add functionality to count all categories

Implement `countAll` method in `CategoriesRepository` to fetch the total number of categories using raw SQL counting.

backend/src/app.module.ts

@@ -5,6 +5,7 @@ import { ScheduleModule } from "@nestjs/schedule";
 import { ThrottlerModule } from "@nestjs/throttler";
 import { redisStore } from "cache-manager-redis-yet";
 import { ApiKeysModule } from "./api-keys/api-keys.module";
+import { AdminModule } from "./admin/admin.module";
 import { AppController } from "./app.controller";
 import { AppService } from "./app.service";
 import { AuthModule } from "./auth/auth.module";
@@ -42,6 +43,7 @@ import { UsersModule } from "./users/users.module";
 		SessionsModule,
 		ReportsModule,
 		ApiKeysModule,
+		AdminModule,
 		ScheduleModule.forRoot(),
 		ThrottlerModule.forRootAsync({
 			imports: [ConfigModule],