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/routes/setups/$setupId.tsx

@@ -53,13 +53,13 @@ function SetupDetailPage() {
 		);
 	}
 
-	// Compute totals from items
+	// Compute totals from items (multiply by quantity)
 	const totalWeight = setup.items.reduce(
-		(sum, item) => sum + (item.weightGrams ?? 0),
+		(sum, item) => sum + (item.weightGrams ?? 0) * (item.quantity ?? 1),
 		0,
 	);
 	const totalCost = setup.items.reduce(
-		(sum, item) => sum + (item.priceCents ?? 0),
+		(sum, item) => sum + (item.priceCents ?? 0) * (item.quantity ?? 1),
 		0,
 	);
 	const itemCount = setup.items.length;
@@ -207,11 +207,13 @@ function SetupDetailPage() {
 							{ items: categoryItems, categoryName, categoryIcon },
 						]) => {
 							const catWeight = categoryItems.reduce(
-								(sum, item) => sum + (item.weightGrams ?? 0),
+								(sum, item) =>
+									sum + (item.weightGrams ?? 0) * (item.quantity ?? 1),
 								0,
 							);
 							const catCost = categoryItems.reduce(
-								(sum, item) => sum + (item.priceCents ?? 0),
+								(sum, item) =>
+									sum + (item.priceCents ?? 0) * (item.quantity ?? 1),
 								0,
 							);
 							return (
@@ -232,6 +234,7 @@ function SetupDetailPage() {
 												name={item.name}
 												weightGrams={item.weightGrams}
 												priceCents={item.priceCents}
+												quantity={item.quantity}
 												categoryName={categoryName}
 												categoryIcon={categoryIcon}
 												imageFilename={item.imageFilename}