feat(bg): add background feed refresh every ~30 min

Registers com.kisani.jarvis.feed.refresh as a BGAppRefreshTask.
On each fire it fetches the latest 40 stories and upserts CachedStory
rows so the SwiftData cache is warm before the user opens the app.
Already-cached rows have signalScore / sourceCount refreshed in-place.

Single ModelContainer owned by JarvisApp and shared via
BackgroundRefreshManager.container to avoid multi-container conflicts.
BG task ID registered in AppDelegate and declared in project.yml.

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

Jarvis/JarvisApp.swift

@@ -8,7 +8,7 @@ import BackgroundTasks
 final class AppDelegate: NSObject, UIApplicationDelegate {
     func application(_ application: UIApplication,
                      didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]? = nil) -> Bool {
-        // Register the briefing background-refresh handler before launch completes.
+        // Briefing notifications refresh
         BGTaskScheduler.shared.register(forTaskWithIdentifier: jarvisBriefingRefreshID, using: nil) { task in
             Task { @MainActor in
                 await NotificationManager.shared.applySettings()
@@ -16,6 +16,13 @@ final class AppDelegate: NSObject, UIApplicationDelegate {
                 task.setTaskCompleted(success: true)
             }
         }
+        // Story feed cache refresh
+        BGTaskScheduler.shared.register(forTaskWithIdentifier: jarvisFeedRefreshID, using: nil) { task in
+            guard let refresh = task as? BGAppRefreshTask else {
+                task.setTaskCompleted(success: false); return
+            }
+            BackgroundRefreshManager.handleFeedRefresh(task: refresh)
+        }
         return true
     }
 }
@@ -31,6 +38,13 @@ struct JarvisApp: App {
     @StateObject private var connManager = ConnectivityManager.shared
     @StateObject private var notifications = NotificationManager.shared
 
+    // Single ModelContainer instance shared with BackgroundRefreshManager.
+    private let container: ModelContainer = {
+        let schema = Schema([CachedStory.self, CachedArticle.self,
+                             ReadStory.self, SavedStory.self, SeenStory.self])
+        return try! ModelContainer(for: schema)
+    }()
+
     var body: some Scene {
         WindowGroup {
             Group {
@@ -48,12 +62,15 @@ struct JarvisApp: App {
             .environmentObject(connManager)
             .environmentObject(notifications)
             .task {
+                // Wire the shared container before scheduling BG work.
+                BackgroundRefreshManager.container = container
+                BackgroundRefreshManager.scheduleFeedRefresh()
+
                 connManager.start()
                 await connManager.resolveAndActivate()
                 await notifications.bootstrap()
             }
         }
-        .modelContainer(for: [CachedStory.self, CachedArticle.self, ReadStory.self,
-                              SavedStory.self, SeenStory.self])
+        .modelContainer(container)
     }
 }