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/database/schemas/content.ts

@@ -12,7 +12,7 @@ import { categories } from "./categories";
 import { tags } from "./tags";
 import { users } from "./users";
 
-export const contentType = pgEnum("content_type", ["meme", "gif"]);
+export const contentType = pgEnum("content_type", ["meme", "gif", "video"]);
 
 export const contents = pgTable(
 	"contents",