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/server/services/setup.service.ts

@@ -21,12 +21,12 @@ export function getAllSetups(db: Db = prodDb) {
         WHERE setup_items.setup_id = setups.id
       ), 0)`.as("item_count"),
 			totalWeight: sql<number>`COALESCE((
-        SELECT SUM(items.weight_grams) FROM setup_items
+        SELECT SUM(items.weight_grams * items.quantity) FROM setup_items
         JOIN items ON items.id = setup_items.item_id
         WHERE setup_items.setup_id = setups.id
       ), 0)`.as("total_weight"),
 			totalCost: sql<number>`COALESCE((
-        SELECT SUM(items.price_cents) FROM setup_items
+        SELECT SUM(items.price_cents * items.quantity) FROM setup_items
         JOIN items ON items.id = setup_items.item_id
         WHERE setup_items.setup_id = setups.id
       ), 0)`.as("total_cost"),
@@ -45,6 +45,7 @@ export function getSetupWithItems(db: Db = prodDb, setupId: number) {
 			name: items.name,
 			weightGrams: items.weightGrams,
 			priceCents: items.priceCents,
+			quantity: items.quantity,
 			categoryId: items.categoryId,
 			notes: items.notes,
 			productUrl: items.productUrl,