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.

tests/test_scheduler.py

@@ -110,8 +110,27 @@ def test_max_iterations_and_validation():
             raise AssertionError(f"应当失败: {tasks}, {kwargs}")
 
 
+def test_next_run_fn_controls_reschedule():
+    clock = [1_000.0]
+    calls = []
+    task = ScheduledTask(
+        "daily", 86400, lambda: calls.append(clock[0]),
+        next_run_fn=lambda started: started + 123,
+    )
+    scheduler = Scheduler([task], clock=lambda: clock[0])
+    scheduler.run_due()
+    assert calls == [1_000.0]
+    assert task.next_run == 1_123.0
+    clock[0] = 1_122.0
+    assert scheduler.run_due() == []
+    clock[0] = 1_123.0
+    scheduler.run_due()
+    assert calls == [1_000.0, 1_123.0]
+
+
 def main():
     test_run_when_due_and_reschedule()
+    test_next_run_fn_controls_reschedule()
     test_task_error_does_not_block_other_tasks()
     test_run_forever_with_stop_event()
     test_max_iterations_and_validation()