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/stats.ts

@@ -31,6 +31,7 @@ export interface Stats {
   series30: { date: string; grams: number }[];
   series90: { date: string; grams: number }[];
   activeCount: number;
+  checkedOutCount: number;
   consumedCount: number;
   goneCount: number;
   archivedCount: number;
@@ -53,7 +54,7 @@ export function computeStats(data: Bootstrap): Stats {
   const items = enrichItems(data);
   const dayKey = (d: Date) => d.toISOString().slice(0, 10);
 
-  const active = items.filter((p) => p.status === "active");
+  const active = items.filter((p) => p.status === "active" || p.status === "checked-out");
   const consumed = items.filter((p) => p.status === "consumed" && p.consumedDate);
   const gone = items.filter((p) => p.status === "gone");
 
@@ -271,7 +272,8 @@ export function computeStats(data: Bootstrap): Stats {
     series7,
     series30,
     series90,
-    activeCount: active.length,
+    activeCount: items.filter((p) => p.status === "active").length,
+    checkedOutCount: items.filter((p) => p.status === "checked-out").length,
     consumedCount: consumed.length,
     goneCount: gone.length,
     archivedCount: consumed.length + gone.length,