feat(media): add image resizing support for processImage

Extend the `processImage` method to support optional resizing with `width` and `height` parameters. Update processing pipeline to handle resizing while maintaining existing format processing for `webp` and `avif`.

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

@@ -17,6 +17,7 @@ export interface IMediaService {
 	processImage(
 		buffer: Buffer,
 		format?: "webp" | "avif",
+		resize?: { width?: number; height?: number },
 	): Promise<MediaProcessingResult>;
 	processVideo(
 		buffer: Buffer,