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/mail.interface.ts

@@ -0,0 +1,4 @@
+export interface IMailService {
+	sendEmailValidation(email: string, token: string): Promise<void>;
+	sendPasswordReset(email: string, token: string): Promise<void>;
+}

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>;
+}

backend/src/common/interfaces/storage.interface.ts

@@ -0,0 +1,39 @@
+import type { Readable } from "node:stream";
+
+export interface IStorageService {
+	uploadFile(
+		fileName: string,
+		file: Buffer,
+		mimeType: string,
+		metaData?: Record<string, string>,
+		bucketName?: string,
+	): Promise<string>;
+
+	getFile(
+		fileName: string,
+		bucketName?: string,
+	): Promise<Readable>;
+
+	getFileUrl(
+		fileName: string,
+		expiry?: number,
+		bucketName?: string,
+	): Promise<string>;
+
+	getUploadUrl(
+		fileName: string,
+		expiry?: number,
+		bucketName?: string,
+	): Promise<string>;
+
+	deleteFile(fileName: string, bucketName?: string): Promise<void>;
+
+	getFileInfo(fileName: string, bucketName?: string): Promise<any>;
+
+	moveFile(
+		sourceFileName: string,
+		destinationFileName: string,
+		sourceBucketName?: string,
+		destinationBucketName?: string,
+	): Promise<string>;
+}