feat: add quantity support to totals, UI, and thread resolution

- totals.service: multiply weight/cost sums by quantity in category and global totals
- setup.service: multiply by quantity in getAllSetups SQL subqueries; expose quantity in getSetupWithItems item list
- thread.service: explicitly pass quantity: 1 when inserting resolved item
- ItemForm: add Quantity number input (min=1, default=1) after price field
- ItemCard: show ×N badge next to item name when quantity > 1
- CollectionView: pass quantity prop to ItemCard in both filtered and grouped views
- $setupId.tsx: pass quantity to ItemCard; multiply by quantity in client-side per-setup totals
- WeightSummaryCard: multiply by quantity in all chart and legend weight calculations
- useItems / useSetups: add quantity to ItemWithCategory / SetupItemWithCategory interfaces

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

src/client/hooks/useItems.ts

@@ -7,6 +7,7 @@ interface ItemWithCategory {
 	name: string;
 	weightGrams: number | null;
 	priceCents: number | null;
+	quantity: number;
 	categoryId: number;
 	notes: string | null;
 	productUrl: string | null;

src/client/hooks/useSetups.ts

@@ -16,6 +16,7 @@ interface SetupItemWithCategory {
 	name: string;
 	weightGrams: number | null;
 	priceCents: number | null;
+	quantity: number;
 	categoryId: number;
 	notes: string | null;
 	productUrl: string | null;