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/Store/StoryStore.swift

@@ -16,10 +16,32 @@ final class StoryStore: ObservableObject {
     @Published var lastSyncedAt: Date?
     @Published var hasMore = false
     @Published var selectedTopic: String? = nil
+    @Published var selectedTags: Set<String> = []
 
     private var nextCursor: String?
     private var refreshTask: Task<Void, Never>?
+    private var foregroundSyncTask: Task<Void, Never>?
     private var cancellables = Set<AnyCancellable>()
+
+    // MARK: - Foreground sync
+
+    /// Call when app becomes active. Polls every 5 min so the feed never runs dry.
+    /// The WebSocket handles real-time events between polls.
+    func startForegroundSync() {
+        foregroundSyncTask?.cancel()
+        foregroundSyncTask = Task { [weak self] in
+            while !Task.isCancelled {
+                try? await Task.sleep(nanoseconds: 5 * 60 * 1_000_000_000)
+                guard !Task.isCancelled else { return }
+                await self?.loadStories(refresh: true)
+            }
+        }
+    }
+
+    func stopForegroundSync() {
+        foregroundSyncTask?.cancel()
+        foregroundSyncTask = nil
+    }
     private let ws = WebSocketManager.shared
     private let api = APIClient.shared
 
@@ -42,7 +64,8 @@ final class StoryStore: ObservableObject {
         do {
             let result = try await api.fetchStories(
                 cursor: cursor,
-                topic: selectedTopic
+                topic: selectedTopic,
+                tags: selectedTags
             )
             stories = refresh ? result.data : stories + result.data
             nextCursor = result.nextCursor
@@ -61,7 +84,7 @@ final class StoryStore: ObservableObject {
         guard hasMore, !isLoadingMore, let cursor = nextCursor else { return }
         isLoadingMore = true
         do {
-            let result = try await api.fetchStories(cursor: cursor, topic: selectedTopic)
+            let result = try await api.fetchStories(cursor: cursor, topic: selectedTopic, tags: selectedTags)
             stories += result.data
             nextCursor = result.nextCursor
             hasMore = result.hasMore
@@ -82,6 +105,14 @@ final class StoryStore: ObservableObject {
 
     func setTopic(_ topic: String?) async {
         selectedTopic = topic
+        selectedTags = []
+        await loadStories(refresh: true)
+    }
+
+    func setPill(_ pill: StoryPill) async {
+        selectedTopic = nil
+        selectedTags = pill.slugs
+        nextCursor = nil
         await loadStories(refresh: true)
     }