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/common/interfaces/media.interface.ts

@@ -0,0 +1,25 @@
+export interface MediaProcessingResult {
+	buffer: Buffer;
+	mimeType: string;
+	extension: string;
+	width?: number;
+	height?: number;
+	size: number;
+}
+
+export interface ScanResult {
+	isInfected: boolean;
+	virusName?: string;
+}
+
+export interface IMediaService {
+	scanFile(buffer: Buffer, filename: string): Promise<ScanResult>;
+	processImage(
+		buffer: Buffer,
+		format?: "webp" | "avif",
+	): Promise<MediaProcessingResult>;
+	processVideo(
+		buffer: Buffer,
+		format?: "webm" | "av1",
+	): Promise<MediaProcessingResult>;
+}