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/components/CollectionView.tsx

@@ -224,6 +224,7 @@ export function CollectionView() {
 								name={item.name}
 								weightGrams={item.weightGrams}
 								priceCents={item.priceCents}
+								quantity={item.quantity}
 								categoryName={item.categoryName}
 								categoryIcon={item.categoryIcon}
 								imageFilename={item.imageFilename}
@@ -257,6 +258,7 @@ export function CollectionView() {
 											name={item.name}
 											weightGrams={item.weightGrams}
 											priceCents={item.priceCents}
+											quantity={item.quantity}
 											categoryName={categoryName}
 											categoryIcon={categoryIcon}
 											imageFilename={item.imageFilename}