fix: finalize durable Pi lifecycle

backend/src/app.ts

@@ -111,12 +111,26 @@ export function buildApp(config: AppConfig, deps?: BuildAppDeps): FastifyInstanc
     maintenanceBarrier,
   });
   app.post("/internal/maintenance/activate", async (req, reply) => {
-    await maintenanceBarrier.activate();
-    return maintenanceBarrier.status();
+    try {
+      await maintenanceBarrier.activate();
+      return maintenanceBarrier.status();
+    } catch {
+      return reply.code(500).send({
+        ...maintenanceBarrier.status(),
+        error: "maintenance activation durability was not acknowledged",
+      });
+    }
   });
   app.post("/internal/maintenance/deactivate", async (req, reply) => {
-    maintenanceBarrier.deactivate();
-    return maintenanceBarrier.status();
+    try {
+      maintenanceBarrier.deactivate();
+      return maintenanceBarrier.status();
+    } catch {
+      return reply.code(500).send({
+        ...maintenanceBarrier.status(),
+        error: "maintenance deactivation durability was not acknowledged",
+      });
+    }
   });
   app.get("/internal/maintenance/status", async (req, reply) => {
     return maintenanceBarrier.status();