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/reports/reports.module.ts

@@ -4,10 +4,11 @@ import { CryptoModule } from "../crypto/crypto.module";
 import { DatabaseModule } from "../database/database.module";
 import { ReportsController } from "./reports.controller";
 import { ReportsService } from "./reports.service";
+import { ReportsRepository } from "./repositories/reports.repository";
 
 @Module({
 	imports: [DatabaseModule, AuthModule, CryptoModule],
 	controllers: [ReportsController],
-	providers: [ReportsService],
+	providers: [ReportsService, ReportsRepository],
 })
 export class ReportsModule {}