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/media/media.module.ts

@@ -1,8 +1,10 @@
 import { Module } from "@nestjs/common";
 import { MediaService } from "./media.service";
+import { ImageProcessorStrategy } from "./strategies/image-processor.strategy";
+import { VideoProcessorStrategy } from "./strategies/video-processor.strategy";
 
 @Module({
-	providers: [MediaService],
+	providers: [MediaService, ImageProcessorStrategy, VideoProcessorStrategy],
 	exports: [MediaService],
 })
 export class MediaModule {}