Adds a toggle button to show/hide the filter panel in Movies, Games,
Mixed, and TV views. On mobile the layout stacks vertically (filter
above content); on md+ it returns to the side-by-side layout. The
toggle button highlights when filters are active so hidden filters
remain discoverable. Also fixes a layout bug where items-start on the
flex-col container caused MixedView thumbnails to collapse on narrow
screens.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
