Add checkout/custody feature for tracking items in personal possession

Items can now be checked out of their bin into "my custody" and later
checked back in or marked consumed. Adds checkout/checkin API endpoints,
a My Custody sidebar page, CheckoutFlow and CheckinFlow modals, and
updates ProductDetail, Inventory, ConsumeFlow, and MarkGoneFlow to
handle the new checked-out status. Bulk items prompt for remaining
weight on check-in.

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

web/src/components/modals/ConsumeFlow.tsx

@@ -21,7 +21,7 @@ export function ConsumeFlow({
   const qc = useQueryClient();
   const { toast } = useToast();
   const allItems = enrichItems(data);
-  const active = allItems.filter((i) => i.status === "active");
+  const active = allItems.filter((i) => i.status === "active" || i.status === "checked-out");
   const [itemId, setItemId] = useState(initialItem?.id ?? "");
   const [rating, setRating] = useState(4);
   const [notes, setNotes] = useState("");