v3: allow users to edit dump thumbnail, fixed some linter errors in the frontend

api/services/follow-service.ts

@@ -24,7 +24,7 @@ import {
 // Mirrors dump-service SELECT_COLS_ALIASED — kept local to avoid circular imports
 const SELECT_COLS_ALIASED =
   "d.id, d.kind, d.title, d.slug, d.comment, d.user_id, d.created_at, d.updated_at, d.url, d.rich_content, " +
-  "d.file_name, d.file_mime, d.file_size, d.vote_count, d.is_private," +
+  "d.file_name, d.file_mime, d.file_size, d.vote_count, d.is_private, d.custom_thumbnail_mime," +
   " (SELECT COUNT(*) FROM comments WHERE dump_id = d.id AND deleted = 0) as comment_count";
 
 // ── Follow / unfollow a user ──────────────────────────────────────────────────