feat: 电商页面 KeepAlive 保活机制，切换页面不再丢失生成状态

通过 display:none 模式实现轻量 KeepAlive，电商页面首次访问后保持挂载，
切换到其他页面再切回时所有右侧面板状态（上传图片、生成进度、结果）完整保留。
同时清理项目中的临时文件和本地冗余图片。

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/services/backgroundTaskRunner.ts

@@ -0,0 +1,128 @@
+import { useGenerationStore, type GenerationQueueItem } from "../stores/useGenerationStore";
+import { aiGenerationClient } from "../api/aiGenerationClient";
+
+type PollCallback = (item: GenerationQueueItem) => void;
+
+const activePollers = new Map<string, ReturnType<typeof setInterval>>();
+const pollCallbacks = new Set<PollCallback>();
+
+const POLL_INTERVAL = 3000;
+const MAX_POLL_ATTEMPTS = 200; // 10 minutes max per task
+
+export function subscribeToTaskUpdates(callback: PollCallback): () => void {
+  pollCallbacks.add(callback);
+  return () => { pollCallbacks.delete(callback); };
+}
+
+function notifyCallbacks(item: GenerationQueueItem): void {
+  pollCallbacks.forEach((cb) => cb(item));
+}
+
+function pollTask(item: GenerationQueueItem, attemptsRef: { current: number }): void {
+  const key = `poll-${item.id}`;
+  if (activePollers.has(key)) return;
+
+  const interval = setInterval(async () => {
+    const current = useGenerationStore.getState().queue.find((i) => i.id === item.id);
+    if (!current || current.status === "completed" || current.status === "failed" || current.status === "cancelled") {
+      cleanupPoll(key);
+      return;
+    }
+
+    attemptsRef.current++;
+    if (attemptsRef.current > MAX_POLL_ATTEMPTS) {
+      useGenerationStore.getState().updateTask(item.id, {
+        status: "failed",
+        error: "任务超时，请重新提交",
+      });
+      notifyCallbacks({ ...item, status: "failed", error: "任务超时，请重新提交" });
+      cleanupPoll(key);
+      return;
+    }
+
+    try {
+      const status = await aiGenerationClient.getTaskStatus(current.taskId || item.taskId || "");
+      const patch: Partial<GenerationQueueItem> = {
+        progress: status.progress,
+        resultUrl: status.resultUrl || current.resultUrl,
+        error: status.error || current.error,
+      };
+
+      if (status.status === "completed") {
+        patch.status = "completed";
+        useGenerationStore.getState().updateTask(item.id, patch);
+        notifyCallbacks({ ...item, ...patch, status: "completed" });
+        cleanupPoll(key);
+      } else if (status.status === "failed" || status.status === "cancelled") {
+        patch.status = "failed";
+        useGenerationStore.getState().updateTask(item.id, patch);
+        notifyCallbacks({ ...item, ...patch, status: "failed" });
+        cleanupPoll(key);
+      } else {
+        patch.status = "running";
+        useGenerationStore.getState().updateTask(item.id, patch);
+        notifyCallbacks({ ...item, ...patch, status: "running" });
+      }
+    } catch {
+      // Network error during poll — keep trying
+    }
+  }, POLL_INTERVAL);
+
+  activePollers.set(key, interval);
+}
+
+function cleanupPoll(key: string): void {
+  const interval = activePollers.get(key);
+  if (interval) {
+    clearInterval(interval);
+    activePollers.delete(key);
+  }
+}
+
+export function startBackgroundPolling(): void {
+  const tasks = useGenerationStore.getState().getRunningTasks();
+  const attemptsMap = new Map<string, { current: number }>();
+
+  tasks.forEach((task) => {
+    if (task.taskId) {
+      if (!attemptsMap.has(task.id)) {
+        attemptsMap.set(task.id, { current: 0 });
+      }
+      pollTask(task, attemptsMap.get(task.id)!);
+    }
+  });
+}
+
+export function resumeTaskPolling(taskId: string, storeId: string): void {
+  const task = useGenerationStore.getState().queue.find((i) => i.id === storeId);
+  if (task && task.status !== "completed" && task.status !== "failed") {
+    pollTask(task, { current: 0 });
+  }
+}
+
+export function stopAllPolling(): void {
+  activePollers.forEach((interval) => clearInterval(interval));
+  activePollers.clear();
+}
+
+// ── Recovery on page load ──────────────────────────
+export function recoverAndResumeTasks(): void {
+  const pendingTasks = useGenerationStore.getState().getRunningTasks();
+  if (!pendingTasks.length) return;
+
+  pendingTasks.forEach((task) => {
+    if (task.taskId) {
+      // Mark as pending so the workbench/ecommerce can re-submit to polling
+      useGenerationStore.getState().updateTask(task.id, { status: "pending" });
+    } else {
+      // No taskId means it was queued but never submitted — mark failed
+      useGenerationStore.getState().updateTask(task.id, {
+        status: "failed",
+        error: "页面刷新后任务丢失，请重新提交",
+      });
+    }
+  });
+
+  // Start polling recovered tasks
+  setTimeout(() => startBackgroundPolling(), 500);
+}