feat(p1): add daily snapshots and fan tracking

Implement P1: seven-metric view snapshots, relation/stat fan snapshots, failure placeholders, resume by daily completion markers, Cookie login warnings, daily SQLite backups, Shanghai daily scheduling, and CLI snapshot/auth-check commands. Real read-only run captured 795/795 videos successfully over 1124s with a verified daily backup.

reaction_board/services/maintenance.py

@@ -0,0 +1,50 @@
+# -*- coding: utf-8 -*-
+"""备份与保留期清理。"""
+
+from __future__ import annotations
+
+import time
+from pathlib import Path
+
+from ..database import Database
+
+
+def daily_backup_path(backup_dir: str | Path, stat_date: str) -> Path:
+    compact = stat_date.replace("-", "")
+    return Path(backup_dir) / f"app-{compact}.db"
+
+
+def backup_daily(
+    db: Database,
+    backup_dir: str | Path,
+    stat_date: str,
+    *,
+    logger=None,
+) -> Path:
+    target = daily_backup_path(backup_dir, stat_date)
+    db.backup_to(target)
+    if logger is not None:
+        logger.info("backup.daily", path=str(target), stat_date=stat_date)
+    return target
+
+
+def prune_daily_backups(
+    backup_dir: str | Path,
+    *,
+    keep_days: int,
+    now: float | None = None,
+) -> list[Path]:
+    """只清理 ``app-YYYYMMDD.db`` 日备份，不动迁移备份。"""
+    target_dir = Path(backup_dir)
+    if not target_dir.is_dir():
+        return []
+    cutoff = (time.time() if now is None else now) - keep_days * 86400
+    removed: list[Path] = []
+    for path in target_dir.glob("app-[0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9].db"):
+        try:
+            if path.stat().st_mtime < cutoff:
+                path.unlink()
+                removed.append(path)
+        except OSError:
+            continue
+    return removed