fix(panel): phase inference fallback for dedup-only harvests

A redundant run (all articles deduped) never rewrites .manifest.json, so
the disk-signal inference stayed at 采集中 during the whole summary/finalize
phase while the browser sat idle. After 10 minutes with no fetch signals,
report 摘要生成(推定) instead.

web/app.py

@@ -599,6 +599,10 @@ def _harvest_phase(source):
         mani = mtime(day_dir / ".manifest.json")
         if mani and mani > start:
             return start, "摘要生成"
+    # 无任何抓取信号(常见于重复采集:文章全被去重,manifest 不重写):
+    # 超过 10 分钟仍无新文件,推定已进入摘要/处理阶段
+    if (datetime.now() - start).total_seconds() > 600:
+        return start, "摘要生成(推定)"
     return start, "采集中"