Keep adoption transfer codes stable

frontend/src/App.tsx

@@ -1665,6 +1665,46 @@ function App() {
     setEditingVeterinaryInfo(false);
   }, [selectedBird]);
 
+  useEffect(() => {
+    const selectedBirdId = selectedBird?.id;
+
+    if (!selectedBirdId || !authToken || adoptionTransferCodes[selectedBirdId]) {
+      return;
+    }
+
+    let canceled = false;
+
+    const loadOpenTransferCode = async () => {
+      try {
+        const response = await apiFetch(`/birds/${selectedBirdId}/transfer-code`, authToken);
+
+        if (!response.ok) {
+          return;
+        }
+
+        const data =
+          (await readJsonSafely<{
+            transferCode?: {
+              code?: string;
+            } | null;
+          }>(response)) ?? {};
+        const code = data.transferCode?.code;
+
+        if (!canceled && code) {
+          setAdoptionTransferCodes((current) => ({ ...current, [selectedBirdId]: code }));
+        }
+      } catch {
+        // Transfer codes are optional until a report/code is created.
+      }
+    };
+
+    void loadOpenTransferCode();
+
+    return () => {
+      canceled = true;
+    };
+  }, [adoptionTransferCodes, authToken, selectedBird?.id]);
+
   const overviewWindowStartDate = useMemo(() => {
     const startDate = new Date();
     startDate.setHours(0, 0, 0, 0);