feat: add real-time collaborative shopping list at /cospend/list

Real-time shopping list with SSE sync between multiple clients, automatic
item categorization using embedding-based classification + Bring icon
matching, and card-based UI with category grouping.

- SSE broadcast for live sync (add/check/remove items across tabs)
- Hybrid categorizer: direct catalog lookup → category-scoped embedding
  search → per-category default icons, with DB caching
- 388 Bring catalog icons matched via multilingual-e5-base embeddings
- 170+ English→German icon aliases for reliable cross-language matching
- Move cospend dashboard to /cospend/dash, /cospend redirects to list
- Shopping icon on homepage links to /cospend/list

src/lib/components/cospend/PaymentModal.svelte

@@ -76,7 +76,7 @@
 
   function closeModal() {
     // Use shallow routing to go back to dashboard without full navigation
-    goto('/cospend', { replaceState: true, noScroll: true, keepFocus: true });
+    goto('/cospend/dash', { replaceState: true, noScroll: true, keepFocus: true });
     onclose?.();
   }