DB-first library reads, mixed library indexing, and manual NFO refresh

- API reads now serve from media_items cache instead of scanning the filesystem
  on every request; scans (manual or scheduled) remain the write path
- NFO metadata is no longer parsed automatically during scans; title falls back
  to folder/filename — metadata can be refreshed per-item via the kabob menu
- Mixed libraries are now indexed in media_items (new mixed_file item type)
  with file_path stored; scanMixed walks recursively and upserts all files
- Added file_path column to media_items and migrated item_type CHECK constraint
  to include mixed_file via safe table-recreation migration
- New POST /api/nfo-refresh endpoint reads the .nfo for a single item and
  patches its DB row (supports movie, tv_series, tv_episode)
- Added "Refresh metadata" button to movie and TV series kabob menus

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/components/movies/MoviesView.tsx

@@ -205,6 +205,7 @@ export default function MoviesView({ libraryId }: Props) {
             onNext={selectedIndex < filtered.length - 1 ? () => setSelectedIndex((i) => (i !== null ? i + 1 : null)) : undefined}
             onTagsChanged={() => { setFilterRefreshKey((k) => k + 1); fetchAssignments() }}
             onDeleted={handleDeleted}
+            onMetadataRefreshed={fetchMovies}
           />
         )}
         </div>