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

frontend/src/lib/components/account/UserBookingModal.svelte

@@ -4,7 +4,6 @@
 	import { toast } from 'svelte-sonner';
 	import * as Modal from '$lib/components/ui/dialog';
 	import { Button } from '$lib/components/ui/button';
-	import { Separator } from '$lib/components/ui/separator';
 
 	interface Props {
 		open: boolean;