后台同步任务超时后可覆盖启动，前端阻塞时显示提示而非静默隐藏

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

ft-app/app/collector.py

@@ -1,13 +1,16 @@
 """Data collector — fetch OHLCV from akshare and upsert into daily_bars."""
 import threading
+import time
 from datetime import date
 from app.database import SessionLocal
 from app.models import DailyBar, Contract
 from app.engine.lock_strategy import compute_amp_5d
 
-_progress = {"running": False, "label": "", "done": 0, "total": 0, "result": 0, "finished": False, "error": ""}
+_progress = {"running": False, "label": "", "done": 0, "total": 0, "result": 0, "finished": False, "error": "", "started_at": 0}
 _lock = threading.Lock()
 
+STALE_SECONDS = 120
+
 
 def get_progress() -> dict:
     with _lock:
@@ -16,9 +19,10 @@ def get_progress() -> dict:
 
 def _start_bg(target, label):
     with _lock:
-        if _progress["running"]:
+        now = time.time()
+        if _progress["running"] and (now - _progress["started_at"]) < STALE_SECONDS:
             return False
-        _progress.update(running=True, finished=False, label=label, done=0, total=0, error="")
+        _progress.update(running=True, finished=False, label=label, done=0, total=0, error="", started_at=now)
 
     def _run():
         try: