feat: add video upload feature with support for validation and processing

- Introduced "video" as a new content type across backend and frontend.
- Updated validation schemas and MIME-type handling for video files.
- Implemented file size limits for videos (10 MB max) in configuration.
- Enhanced upload flow with auto-detection of file types (image, GIF, video).
- Expanded media processing to handle video files and convert them to WebM format.

backend/src/contents/dto/upload-content.dto.ts

@@ -11,7 +11,7 @@ import { ContentType } from "./create-content.dto";
 
 export class UploadContentDto {
 	@IsEnum(ContentType)
-	type!: "meme" | "gif";
+	type!: "meme" | "gif" | "video";
 
 	@IsString()
 	@IsNotEmpty()