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.

frontend/src/types/content.ts

@@ -7,7 +7,7 @@ export interface Content {
 	description?: string;
 	url: string;
 	thumbnailUrl?: string;
-	type: "meme" | "gif";
+	type: "meme" | "gif" | "video";
 	mimeType: string;
 	size: number;
 	width?: number;