feat(background-task): 实现原生与JS层的任务同步机制

解决后台任务在JS监听器未就绪时丢失的问题。新增任务缓存队列，当检测到无JS监听器时将任务暂存，并启动20秒超时计时器等待JS初始化完成。JS层通过markJSReady接口通知原生层准备就绪，触发缓存任务的立即执行。超时后自动切换到默认处理逻辑，确保任务不丢失。

ios/OutLive/BackgroundTaskBridge.m

@@ -28,4 +28,7 @@ RCT_EXTERN_METHOD(backgroundRefreshStatus:(RCTPromiseResolveBlock)resolver
 RCT_EXTERN_METHOD(simulateLaunch:(RCTPromiseResolveBlock)resolver
                   rejecter:(RCTPromiseRejectBlock)rejecter)
 
+RCT_EXTERN_METHOD(markJSReady:(RCTPromiseResolveBlock)resolver
+                  rejecter:(RCTPromiseRejectBlock)rejecter)
+
 @end

ios/OutLive/BackgroundTaskBridge.swift

@@ -27,6 +27,10 @@ class BackgroundTaskBridge: RCTEventEmitter {
   private var requiresExternalPower = false
   private var defaultDelay: TimeInterval = 60 * 30 // 30 minutes
   private var currentTask: BGTask?
+  private let pendingTaskWaitTimeout: TimeInterval = 20
+  private var waitingForJSListeners = false
+  private var pendingTaskPayload: [String: Any]?
+  private var pendingTaskTimeoutWorkItem: DispatchWorkItem?
 
   override init() {
     super.init()
@@ -49,6 +53,9 @@ class BackgroundTaskBridge: RCTEventEmitter {
 
   override func startObserving() {
     hasListeners = true
+    queue.async { [weak self] in
+      self?.emitPendingTaskIfPossible()
+    }
   }
 
   override func stopObserving() {
@@ -345,6 +352,22 @@ class BackgroundTaskBridge: RCTEventEmitter {
     #endif
   }
 
+  @objc
+  func markJSReady(
+    _ resolver: @escaping RCTPromiseResolveBlock,
+    rejecter: @escaping RCTPromiseRejectBlock
+  ) {
+    queue.async { [weak self] in
+      guard let self else { return }
+
+      let hadPendingTask = self.waitingForJSListeners && self.pendingTaskPayload != nil
+      self.emitPendingTaskIfPossible()
+      resolver([
+        "pendingTaskFlushed": hadPendingTask
+      ])
+    }
+  }
+
   // MARK: - Private helpers
 
   @available(iOS 13.0, *)
@@ -408,6 +431,11 @@ class BackgroundTaskBridge: RCTEventEmitter {
       self.currentTask = task
       NSLog("[BackgroundTaskBridge] 开始处理后台任务: \(task.identifier)")
 
+      if self.identifier == nil {
+        self.identifier = task.identifier
+        NSLog("[BackgroundTaskBridge] 使用任务标识符初始化 identifier: \(task.identifier)")
+      }
+
       // 设置任务过期处理器
       task.expirationHandler = { [weak self] in
         guard let self else { return }
@@ -435,28 +463,29 @@ class BackgroundTaskBridge: RCTEventEmitter {
         }
       }
 
+      let payload: [String: Any] = [
+        "identifier": self.identifier ?? task.identifier,
+        "timestamp": Date().timeIntervalSince1970 * 1000
+      ]
+
       guard self.hasListeners else {
-        NSLog("[BackgroundTaskBridge] 没有JS监听器，执行默认处理并重新调度")
-        // 即使没有JS监听器，也要执行基本的任务处理
-        self.executeDefaultTaskAndReschedule()
+        NSLog("[BackgroundTaskBridge] 暂无 JS 监听器，等待 JS 初始化 (最多 \(Int(self.pendingTaskWaitTimeout)) 秒)")
+        self.cacheTaskForLater(payload: payload)
         return
       }
 
       NSLog("[BackgroundTaskBridge] 发送后台任务执行事件到JS")
-      DispatchQueue.main.async {
-        self.sendEvent(
-          withName: "BackgroundTaskBridge.execute",
-          body: [
-            "identifier": self.identifier ?? "",
-            "timestamp": Date().timeIntervalSince1970 * 1000
-          ]
-        )
-      }
+      self.emitTaskToJS(payload: payload)
     }
   }
   
   @available(iOS 13.0, *)
   private func executeDefaultTaskAndReschedule() {
+    waitingForJSListeners = false
+    pendingTaskPayload = nil
+    pendingTaskTimeoutWorkItem?.cancel()
+    pendingTaskTimeoutWorkItem = nil
+
     // 执行默认的后台任务逻辑（当没有JS监听器时）
     NSLog("[BackgroundTaskBridge] 执行默认后台任务逻辑")
     
@@ -506,4 +535,48 @@ class BackgroundTaskBridge: RCTEventEmitter {
       }
     }
   }
+
+  private func cacheTaskForLater(payload: [String: Any]) {
+    waitingForJSListeners = true
+    pendingTaskPayload = payload
+
+    pendingTaskTimeoutWorkItem?.cancel()
+
+    let timeoutItem = DispatchWorkItem { [weak self] in
+      guard let self else { return }
+      guard self.waitingForJSListeners else { return }
+
+      NSLog("[BackgroundTaskBridge] 等待 JS 监听器超时，执行默认处理")
+      self.waitingForJSListeners = false
+      self.pendingTaskPayload = nil
+      self.pendingTaskTimeoutWorkItem = nil
+      self.executeDefaultTaskAndReschedule()
+    }
+
+    pendingTaskTimeoutWorkItem = timeoutItem
+    queue.asyncAfter(deadline: .now() + pendingTaskWaitTimeout, execute: timeoutItem)
+  }
+
+  private func emitPendingTaskIfPossible() {
+    guard hasListeners else { return }
+    guard waitingForJSListeners, let payload = pendingTaskPayload else { return }
+
+    pendingTaskTimeoutWorkItem?.cancel()
+    pendingTaskTimeoutWorkItem = nil
+    waitingForJSListeners = false
+    pendingTaskPayload = nil
+
+    NSLog("[BackgroundTaskBridge] JS 监听器已就绪，发送缓存的后台任务事件")
+    emitTaskToJS(payload: payload)
+  }
+
+  private func emitTaskToJS(payload: [String: Any]) {
+    DispatchQueue.main.async { [weak self] in
+      guard let self else { return }
+      self.sendEvent(
+        withName: "BackgroundTaskBridge.execute",
+        body: payload
+      )
+    }
+  }
 }