feat: keep MOV in video allow-list, drop only WebM

Previous attempt dropped both video/quicktime and video/webm citing
narrow platform support. Re-investigated:

- Modern .mov files (iPhone recordings, screen captures) are ISO BMFF
  containers — the same format MP4 uses. Social platforms decode them
  like MP4 even when PHP's mime_content_type() reports
  'video/quicktime'. Postiz quietly accepts MOV via this same trick:
  their file-type lib detects the magic bytes as 'video/mp4' and
  renames the upload before storage.

- WebM is genuinely incompatible (Matroska + VP8/VP9 stack) — X / IG /
  TikTok / FB / Pinterest / Bluesky / Threads all reject it.

So allow MOV, keep WebM out. Rejecting MOV would force every iPhone
user to transcode before uploading — real UX cost for no gain since
the publishers handle it.

app/Enums/Media/Type.php

@@ -18,20 +18,32 @@ public function label(): string
     }
 
     /**
+     * Allow-list of MIME types we accept on upload / URL fetch.
+     *
+     * Video accepts MP4 plus QuickTime/MOV. Modern .mov files (iPhone
+     * recordings, screen captures) are ISO BMFF containers — the same
+     * format MP4 uses — so social platforms decode them like MP4 even
+     * if PHP reports `video/quicktime`. Accepting MOV avoids forcing
+     * iPhone users to transcode before uploading.
+     *
+     * WebM is rejected: X / IG / TikTok / FB / Pinterest / Bluesky /
+     * Threads all reject the Matroska + VP8/VP9 stack. Without
+     * server-side transcoding, accepting WebM would just produce
+     * platform-specific publish failures down the line.
+     *
      * @return array<int, string>
      */
     public function allowedMimeTypes(): array
     {
         return match ($this) {
             self::Image => ['image/jpeg', 'image/png', 'image/gif', 'image/webp'],
-            self::Video => ['video/mp4', 'video/quicktime', 'video/webm'],
+            self::Video => ['video/mp4', 'video/quicktime'],
         };
     }
 
     /**
-     * Filename extensions that match this type. Used by callers that
-     * validate by name (chunked upload, URL fetch fallback) instead of
-     * by MIME.
+     * Filename extensions that match this type. Mirrors allowedMimeTypes
+     * for callers that validate by name instead of MIME.
      *
      * @return array<int, string>
      */
@@ -39,7 +51,7 @@ public function extensions(): array
     {
         return match ($this) {
             self::Image => ['jpg', 'jpeg', 'png', 'gif', 'webp'],
-            self::Video => ['mp4', 'mov', 'webm'],
+            self::Video => ['mp4', 'mov'],
         };
     }