Portfolio: add filtering, URL sharing, and improved tag input

- Add category filters with dynamic counts that reduce as filters
  applied
- Add ?filter[category]=value URL params for filterable links
- Add ?img= timestamp param that bypasses filters to show specific image
- Update URL when opening/navigating/closing modal for shareable links
- Backend: add /api/portfolio/filters endpoint with filter logic
- Backend: add timestamp lookup fallback for GetImage endpoint
  Frontend:
- Portfolio page: filter dropdowns, keyboard nav, mobile improvements
- ImageUpload: live tag suggestions from API, arrow/Tab navigation,
  confirmation modal before upload, mobile-optimized touch targets
- Add scrollbar-hide utility and fix filter dropdown overflow
- Move Clear all button, add vertical separator on desktop

README.md

@@ -169,6 +169,7 @@ docker compose exec backend sh
 | VAT System | ✅ | ❌ | `get_vat_return_data()`, `calculate_vat()` functions exist |
 | User Referrals | ✅ | ❌ | `user_referrals` table, backend logic exists |
 | Token Refresh | ✅ | ✅ | POST /api/refresh-token, auto-refresh in auth store |
+| Portfolio System | ✅ | ✅ | S3/R2 storage abstraction, tag-based filtering, category filters, admin upload, ?img= featured image param |
 
 ### ⚠️ Partially Complete
 
@@ -185,7 +186,6 @@ docker compose exec backend sh
 |---------|------|-------|
 | Social Auth | `handlers/auth/social.go` | OAuth integration placeholder |
 | Analytics | `handlers/admin/analytics.go` | Statistics/dashboard endpoint |
-| Portfolio Images | `handlers/portfolio/images.go` | Gallery management |
 
 ### 🚧 Critical TODOs
 
@@ -203,7 +203,6 @@ docker compose exec backend sh
 |---------|-------------|
 | One-off Custom Services | Allow creating single-use services not in regular catalog |
 | One-off Exceptional Hours | Single-day overrides without creating a group |
-| S3/R2 Image Hosting | Portfolio image storage with admin upload |
 
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