replace Tailwind in content + collection, remove shop Tailwind entirely (Phase 5c)

- Replace all Tailwind utilities in content.ex and collection.ex with
  semantic CSS classes (content body, contact form, cards, reviews, etc.)
- Delete app-shop.css (Tailwind shop entry point)
- Remove shop Tailwind config from config.exs, dev.exs, mix.exs
- Remove shop Tailwind stylesheet link from shop_root.html.heex
- Add collection filter bar, empty state, and select dropdown styles
- Fix filter pill sizing (use theme font vars instead of hardcoded rem)
- Fix active pill contrast (tinted accent background + dark accent text)
- Fix --t-text-on-accent fallback for pill legibility
- Add padding/font-size to .themed-select

Shop pages now use zero Tailwind. Admin Tailwind remains for Phase 6.

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

PROGRESS.md

@@ -66,7 +66,7 @@ Plans: [admin-redesign.md](docs/plans/admin-redesign.md) | [setup-wizard.md](doc
 | ~~34~~ | ~~Phase 2: Extract product inline styles~~ | 33 | 3h | done |
 | ~~35~~ | ~~Phase 3: Extract layout + cart inline styles~~ | 33 | 3h | done |
 | ~~36~~ | ~~Phase 4: Extract content + template inline styles~~ | 33 | 2.5h | done |
-| 37 | Phase 5: Remove Tailwind from shop | 34-36 | 3h | |
+| ~~37~~ | ~~Phase 5: Remove Tailwind from shop pages~~ | 34-36 | 3h | done |
 | 38 | Phase 6: Replace DaisyUI (admin) | 37 | 3h | |
 | 39 | Phase 7: Remove Tailwind entirely | 38 | 1.5h | |
 | 40 | Phase 8: Optimisation + modern enhancements | 39 | 2.5h | |