admin: fix drink-order reorder race under rapid clicks

BarDrinkEditor derived selected drink order straight from the bar prop,
which only refreshes once a fire-and-forget PATCH's reload() lands. A
second reorder/add/remove click before that round-trip completed
re-derived from the same stale array the first click started from, so
whichever PATCH the server applied last silently won and discarded the
rest.

Track our own in-flight edits in local pendingIds state so back-to-back
clicks chain off each other instead of the lagging prop; it resets to
null (defer to the prop) whenever a fresh bar.drink_ids comes back,
whether that's our own round-trip landing or an edit from elsewhere.

client/src/admin/Admin.tsx

@@ -211,7 +211,23 @@ function BarDrinkEditor({
   onChange: (ids: number[]) => void;
 }) {
   const byId = new Map(allDrinks.map(d => [d.id, d]));
-  const selected = bar.drink_ids.filter(id => {
+
+  // `onChange` fires a fire-and-forget PATCH (see Bars.patch) that only
+  // resolves into a fresh `bar` prop once its `reload()` completes. Deriving
+  // `selected` straight from `bar.drink_ids` meant a second click before that
+  // round-trip landed re-derived its reorder/add/remove from the same stale
+  // array the first click started from — whichever PATCH the server applied
+  // last won, silently discarding the rest. `pendingIds` tracks our own
+  // in-flight optimistic state so back-to-back clicks chain off each other
+  // instead of the lagging prop; it's cleared whenever the server sends back
+  // a fresh `bar.drink_ids` (our own round-trip landing, or an edit from
+  // elsewhere), deferring to that as the new source of truth.
+  const [pendingIds, setPendingIds] = useState<number[] | null>(null);
+  useEffect(() => {
+    setPendingIds(null);
+  }, [bar.drink_ids]);
+
+  const selected = (pendingIds ?? bar.drink_ids).filter(id => {
     const d = byId.get(id);
     return d && !d.archived;
   });
@@ -220,18 +236,22 @@ function BarDrinkEditor({
   const dragFrom = useRef<number | null>(null);
   const [dragOver, setDragOver] = useState<number | null>(null);
 
+  function commit(next: number[]) {
+    setPendingIds(next);
+    onChange(next);
+  }
   function remove(idx: number) {
-    onChange(selected.filter((_, i) => i !== idx));
+    commit(selected.filter((_, i) => i !== idx));
   }
   function add(id: number) {
-    onChange([...selected, id]);
+    commit([...selected, id]);
   }
   function reorder(from: number, to: number) {
     if (from === to || from < 0 || to < 0 || from >= selected.length || to >= selected.length) return;
     const next = selected.slice();
     const [moved] = next.splice(from, 1);
     next.splice(to, 0, moved!);
-    onChange(next);
+    commit(next);
   }
 
   return (