Card Image Caching, Search Cancel Fix, and Loading Spinner

Staging release — try it at staging.arcanetable.app.

Fixes

• Search cancel — clearing the search field or deselecting all type filters now cancels any pending debounced search, so stale results no longer flash in after you've already cleared the input.
• Card image edge caching — removed the Vary header from image responses on the MTG scry server, which was preventing Cloudflare from caching card images at the edge. Card images should now cache and load significantly faster.

Improvements

• The "Loading more results" indicator in the deck editor is now a proper animated spinner instead of plain text, and uses the correct page field to determine when more results are available.