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/strategies/video-processor.strategy.ts

@@ -0,0 +1,71 @@
+import { readFile, unlink, writeFile } from "node:fs/promises";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+import { BadRequestException, Injectable, Logger } from "@nestjs/common";
+import ffmpeg from "fluent-ffmpeg";
+import { v4 as uuidv4 } from "uuid";
+import type { MediaProcessingResult } from "../../common/interfaces/media.interface";
+import type { IMediaProcessorStrategy } from "./media-processor.strategy";
+
+@Injectable()
+export class VideoProcessorStrategy implements IMediaProcessorStrategy {
+	private readonly logger = new Logger(VideoProcessorStrategy.name);
+
+	canHandle(mimeType: string): boolean {
+		return mimeType.startsWith("video/");
+	}
+
+	async process(
+		buffer: Buffer,
+		options: { format: "webm" | "av1" } = { format: "webm" },
+	): Promise<MediaProcessingResult> {
+		const { format } = options;
+		const tempInput = join(tmpdir(), `${uuidv4()}.tmp`);
+		const tempOutput = join(
+			tmpdir(),
+			`${uuidv4()}.${format === "av1" ? "mp4" : "webm"}`,
+		);
+
+		try {
+			await writeFile(tempInput, buffer);
+
+			await new Promise<void>((resolve, reject) => {
+				let command = ffmpeg(tempInput);
+
+				if (format === "webm") {
+					command = command
+						.toFormat("webm")
+						.videoCodec("libvpx-vp9")
+						.audioCodec("libopus")
+						.outputOptions("-crf 30", "-b:v 0");
+				} else {
+					command = command
+						.toFormat("mp4")
+						.videoCodec("libaom-av1")
+						.audioCodec("libopus")
+						.outputOptions("-crf 34", "-b:v 0", "-strict experimental");
+				}
+
+				command
+					.on("end", () => resolve())
+					.on("error", (err) => reject(err))
+					.save(tempOutput);
+			});
+
+			const processedBuffer = await readFile(tempOutput);
+
+			return {
+				buffer: processedBuffer,
+				mimeType: format === "av1" ? "video/mp4" : "video/webm",
+				extension: format === "av1" ? "mp4" : "webm",
+				size: processedBuffer.length,
+			};
+		} catch (error) {
+			this.logger.error(`Error processing video: ${error.message}`);
+			throw new BadRequestException("Failed to process video");
+		} finally {
+			await unlink(tempInput).catch(() => {});
+			await unlink(tempOutput).catch(() => {});
+		}
+	}
+}