feat(offline): persisted query cache + unreachable banner (web + mobile) (#70)

* feat(offline): persisted query cache + unreachable banner (web + mobile)

- Web: PersistQueryClientProvider on localStorage (24h maxAge); mobile:
  AsyncStorage persister (7d). Both exclude high-churn keys (logs,
  notifications, metrics) — stale tails are worse than none.
- networkMode 'offlineFirst' so cached data serves while the refetch
  attempt fails.
- Web: ConnectivityBanner in PlatformShell pings public /health every
  15s + listens to online/offline events — slim "last-known data" bar
  so persisted state can't masquerade as live.
- Mobile: same banner in the tabs layout — /health ping plus
  expo-network's local signal distinguishes "no connection" from
  "instance down".

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

* feat(mobile): cron jobs screen — schedules, run-now, execution history

- /service/cron lists the service's jobs with schedule, timezone,
  last/next run, and last status; "Run now" triggers via the existing
  POST /cron-jobs/:id/trigger and "History" expands recent executions
  with status + output/error.
- Manage row on the service detail + Stack registration.

Verified live: created */5 job on a running service, triggered it —
execution recorded with status success and captured stdout.

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

---------

Co-authored-by: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

app/mobile/src/app/(tabs)/_layout.tsx

@@ -1,10 +1,39 @@
 import React from 'react';
+import { StyleSheet, Text, View } from 'react-native';
 import { Tabs } from 'expo-router';
 import { Ionicons } from '@expo/vector-icons';
 import { useQuery } from '@tanstack/react-query';
+import * as Network from 'expo-network';
 import { useApi } from '../../session';
 import { colors } from '../../theme';
 
+// OfflineBanner pings /health every 15s; expo-network gives a fast local
+// signal, the ping catches "device online but instance down".
+function OfflineBanner() {
+  const api = useApi();
+  const net = useQuery({
+    queryKey: ['connectivity', 'net'],
+    queryFn: async () => (await Network.getNetworkStateAsync()).isConnected !== false,
+    refetchInterval: 15_000,
+  });
+  const ping = useQuery({
+    queryKey: ['connectivity', 'ping'],
+    queryFn: () => api.ping(),
+    refetchInterval: 15_000,
+    retry: 0,
+    networkMode: 'always',
+  });
+  if (net.data !== false && ping.data !== false && !ping.isError) return null;
+  return (
+    <View style={styles.banner}>
+      <Ionicons name="cloud-offline-outline" size={13} color={colors.warn} />
+      <Text style={styles.bannerText}>
+        {net.data === false ? 'No connection' : 'Instance unreachable'} — showing last-known data
+      </Text>
+    </View>
+  );
+}
+
 export default function TabsLayout() {
   const api = useApi();
   const notifs = useQuery({
@@ -15,7 +44,9 @@ export default function TabsLayout() {
   const unread = notifs.data?.unread ?? 0;
 
   return (
-    <Tabs
+    <View style={{ flex: 1 }}>
+      <OfflineBanner />
+      <Tabs
       screenOptions={{
         headerStyle: { backgroundColor: colors.bg },
         headerTintColor: colors.text,
@@ -70,6 +101,21 @@ export default function TabsLayout() {
           ),
         }}
       />
-    </Tabs>
+      </Tabs>
+    </View>
   );
 }
+
+const styles = StyleSheet.create({
+  banner: {
+    flexDirection: 'row',
+    alignItems: 'center',
+    justifyContent: 'center',
+    gap: 6,
+    paddingVertical: 6,
+    backgroundColor: colors.surface,
+    borderBottomWidth: 1,
+    borderBottomColor: colors.warn,
+  },
+  bannerText: { color: colors.textDim, fontSize: 11 },
+});