fix(frontend): resolve build-blocking lint and type errors

next build runs ESLint + full type-check and fails on errors (not just
warnings) - the production build was broken. Fixes: unused imports/vars,
any-typed diff/preference lookups replaced with the actual union/Record
types, ternary-as-statement flagged by no-unused-expressions, unescaped
JSX entities, a UserPreferences interface missing two fields the video
editor already reads/writes at runtime, and an import of
ColumnVisibilityState which @tanstack/react-table does not export
(the real name is VisibilityState).

frontend/src/app/(dashboard)/videos/PushPendingModal.tsx

@@ -38,8 +38,7 @@ function TagsDiff({ before, after }: { before: string[]; after: string[] }) {
 
 function DiffRow({ field, item }: { field: string; item: PushPendingPreviewItem }) {
   const label = FIELD_LABELS[field] ?? field;
-  const diff = item.diff as any;
-  const d = diff[field];
+  const d = item.diff[field as keyof typeof item.diff];
   if (!d) return null;
 
   if (field === 'tags') {
@@ -47,7 +46,7 @@ function DiffRow({ field, item }: { field: string; item: PushPendingPreviewItem
       <tr>
         <td className={styles.diffField}>{label}</td>
         <td className={styles.diffBefore}>{(d.before as string[]).join(', ') || '—'}</td>
-        <td className={styles.diffAfter}><TagsDiff before={d.before} after={d.after} /></td>
+        <td className={styles.diffAfter}><TagsDiff before={d.before as string[]} after={d.after as string[]} /></td>
       </tr>
     );
   }
@@ -60,7 +59,7 @@ function DiffRow({ field, item }: { field: string; item: PushPendingPreviewItem
       </tr>
     );
   }
-  const fmt = (v: any) => {
+  const fmt = (v: string | number | boolean | string[] | null | undefined) => {
     if (v === null || v === undefined) return '—';
     if (typeof v === 'boolean') return v ? 'Yes' : 'No';
     return String(v);