feat: automatic foreground sync — 5 min timer + resume refresh

StoryStore gains startForegroundSync() / stopForegroundSync():
- Polls loadStories(refresh:true) every 5 minutes while app is active
- WebSocket handles real-time storyCreated events between polls
- Timer cancels when app goes to background to save battery

JarvisApp wires scenePhase:
- .active  → start 5-min timer; immediate refresh if last sync > 2 min ago
- .background → cancel timer
- On launch → timer starts after setup completes

Net result: feed replenishes automatically; user never hits an empty list.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Jarvis/JarvisApp.swift

@@ -82,6 +82,7 @@ struct JarvisApp: App {
     @StateObject private var connectivity = ConnectivitySettings.shared
     @StateObject private var connManager = ConnectivityManager.shared
     @StateObject private var notifications = NotificationManager.shared
+    @Environment(\.scenePhase) private var scenePhase
     @State private var splashDone = false
 
     // Single ModelContainer instance shared with BackgroundRefreshManager.
@@ -120,6 +121,22 @@ struct JarvisApp: App {
                 connManager.start()
                 await connManager.resolveAndActivate()
                 await notifications.bootstrap()
+                store.startForegroundSync()
+            }
+            .onChange(of: scenePhase) { _, phase in
+                switch phase {
+                case .active:
+                    store.startForegroundSync()
+                    // Refresh immediately if we've been away more than 2 minutes.
+                    if let last = store.lastSyncedAt,
+                       Date().timeIntervalSince(last) > 120 {
+                        Task { await store.loadStories(refresh: true) }
+                    }
+                case .background:
+                    store.stopForegroundSync()
+                default:
+                    break
+                }
             }
         }
         .modelContainer(container)