feat(scheduler): persist task state/progress/due_at across restart (#8)

Replace process-start next_run=0 guesses with kv task:state records
(status, due_at, stat_date, progress). Startup recovers stale running,
honors future due_at for delayed retries, and resumes the same
stat_date. Seed only enqueues evening seal; seal force keeps non-seed
ok=1 as progress (keep_scraped). Keeps !7 fail-logging and cleanup retry.

reaction_board/web/queries.py

@@ -1983,6 +1983,22 @@ class DashboardQueries:
             }
             retry_seconds = 300
             seed_retry_seconds = 600
+            # 优先 task:state.due_at（跨重启唯一时间门闩）；无则回退 task:last 推导。
+            state_rows = conn.execute(
+                "SELECT k, v FROM kv WHERE k LIKE 'task:state:%'"
+            ).fetchall()
+            for row in state_rows:
+                key = str(row["k"]).removeprefix("task:state:")
+                ui_name = "discover" if key == "discovery" else key
+                if ui_name not in next_runs:
+                    continue
+                try:
+                    state = json.loads(str(row["v"]))
+                    due = float(state.get("due_at") or 0)
+                except (TypeError, ValueError, json.JSONDecodeError):
+                    continue
+                if due > 0:
+                    next_runs[ui_name] = int(due)
             for name, key, at in (
                 ("fans", "fans", cfg.schedule.snapshot_at),
                 ("snapshot", "snapshot", cfg.schedule.snapshot_at),
@@ -1990,6 +2006,14 @@ class DashboardQueries:
                 ("discover", "discovery", None),
                 ("snapshot_recent", "snapshot_recent", None),
             ):
+                # 已有落盘 due_at 则不再用 last 覆盖
+                state_raw = self._kv(conn, f"task:state:{key}")
+                if state_raw:
+                    try:
+                        if float(json.loads(state_raw).get("due_at") or 0) > 0:
+                            continue
+                    except (TypeError, ValueError, json.JSONDecodeError):
+                        pass
                 record = tasks.get(key)
                 if not (isinstance(record, dict) and record.get("finished_at")):
                     continue