feat: add modular services and repositories for improved code organization

Introduce repository pattern across multiple services, including `favorites`, `tags`, `sessions`, `reports`, `auth`, and more. Decouple crypto functionalities into modular services like `HashingService`, `JwtService`, and `EncryptionService`. Improve testability and maintainability by simplifying dependencies and consolidating utility logic.

backend/src/auth/auth.module.ts

@@ -6,11 +6,12 @@ import { UsersModule } from "../users/users.module";
 import { AuthController } from "./auth.controller";
 import { AuthService } from "./auth.service";
 import { RbacService } from "./rbac.service";
+import { RbacRepository } from "./repositories/rbac.repository";
 
 @Module({
 	imports: [UsersModule, CryptoModule, SessionsModule, DatabaseModule],
 	controllers: [AuthController],
-	providers: [AuthService, RbacService],
+	providers: [AuthService, RbacService, RbacRepository],
 	exports: [AuthService, RbacService],
 })
 export class AuthModule {}