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/ProductDetail.tsx

@@ -15,6 +15,8 @@ export function ProductDetail({
   onMarkGone,
   onAudit,
   onEdit,
+  onCheckout,
+  onCheckin,
 }: {
   item: Item;
   data: Bootstrap;
@@ -23,6 +25,8 @@ export function ProductDetail({
   onMarkGone: (i: Item) => void;
   onAudit: (i: Item) => void;
   onEdit: (i: Item) => void;
+  onCheckout: (i: Item) => void;
+  onCheckin: (i: Item) => void;
 }) {
   const bin = data.bins.find((b) => b.id === item.binId);
   const cfg = TYPES.find((t) => t.id === item.type);
@@ -34,6 +38,7 @@ export function ProductDetail({
   const sinceCheck = helpers.daysSinceCheck(item, TODAY_STR);
 
   const isActive = item.status === "active";
+  const isCheckedOut = item.status === "checked-out";
 
   useEffect(() => {
     const handleKeyDown = (e: KeyboardEvent) => {
@@ -58,7 +63,7 @@ export function ProductDetail({
     ["Shop", helpers.shopName(data, item.shopId)],
     ["Total cannabinoids", `${item.totalCannabinoids.toFixed(1)}%`],
     ["Purchase date", fmt.date(item.purchaseDate)],
-    ["Bin", bin ? bin.name : <span style={{ color: "var(--ink-3)" }}>—</span>],
+    ["Bin", isCheckedOut ? "In your custody" : bin ? bin.name : <span style={{ color: "var(--ink-3)" }}>—</span>],
     ["Audit cadence", `Every ${cfg?.cadenceDays ?? "—"} days · ${cfg?.auditMode ?? "—"}`],
     [
       "Cost per gram",
@@ -69,6 +74,9 @@ export function ProductDetail({
           : "—",
     ],
   ];
+  if (item.status === "checked-out") {
+    detailRows.push(["Checked out", fmt.date(item.checkoutDate)]);
+  }
   if (item.status === "consumed") {
     detailRows.push(
       ["Date finished", fmt.date(item.consumedDate)],
@@ -130,17 +138,27 @@ export function ProductDetail({
             Inventory · <span className="mono">{item.assetId}</span>
           </div>
           <div style={{ display: "flex", gap: 6, flexWrap: "wrap", justifyContent: "flex-end" }}>
+            {isActive && (
+              <Btn variant="ghost" icon="pocket" onClick={() => onCheckout(item)}>
+                Check out
+              </Btn>
+            )}
             {isActive && (
               <Btn variant="ghost" icon="check" onClick={() => onAudit(item)}>
                 Audit
               </Btn>
             )}
-            {isActive && (
+            {isCheckedOut && (
+              <Btn variant="sage" icon="check" onClick={() => onCheckin(item)}>
+                Check in
+              </Btn>
+            )}
+            {(isActive || isCheckedOut) && (
               <Btn variant="secondary" icon="check" onClick={() => onConsume(item)}>
                 Mark consumed
               </Btn>
             )}
-            {isActive && (
+            {(isActive || isCheckedOut) && (
               <Btn variant="ghost" icon="bin" onClick={() => onMarkGone(item)} />
             )}
             <Btn variant="ghost" icon="edit" onClick={() => onEdit(item)} />
@@ -159,6 +177,9 @@ export function ProductDetail({
             {item.status === "gone" && (
               <Pill tone="amber">Gone · {fmt.daysAgo(item.goneDate)}</Pill>
             )}
+            {isCheckedOut && (
+              <Pill tone="outline">Checked out · {fmt.daysAgo(item.checkoutDate)}</Pill>
+            )}
             {isActive && overdue && <Pill tone="amber">Audit overdue · {sinceCheck}d</Pill>}
           </div>
           <h1
@@ -214,7 +235,7 @@ export function ProductDetail({
             ))}
           </div>
 
-          {isActive && (
+          {(isActive || isCheckedOut) && (
             <div style={{ marginTop: 20 }}>
               <div
                 style={{