Brings the Flutter discover screen toward web-Koja parity. Unverified (pub blocked).
- DiscoverFilters is now a copyWith class so the many optional filters set safely.
- Adds an "open now" chip, rating chips, sort, and a taxonomy-driven filter sheet
(themes/vibes/occasions/space-features as multi-select chips + price tier),
feeding the rich discover() query. Active-filter badge + pull-to-refresh.
- Café cards show open/closed status.