fix(web): align trend ranges, next runs and preview task records

tests/test_cli.py

@@ -194,6 +194,34 @@ def test_run_once_offline():
             db.close()
 
 
+def test_serve_preview_guard():
+    with tempfile.TemporaryDirectory() as tmp:
+        path = write_config(tmp)
+        assert run_cli(["init", "--config", str(path)])[0] == 0
+        db_path = Path(tmp) / "app.db"
+        try:
+            cli._assert_preview_database(db_path)
+        except cli.ConfigError as exc:
+            assert "preview:seeded" in str(exc)
+        else:
+            raise AssertionError("普通数据库不应通过 --preview 校验")
+
+        db = Database(db_path)
+        db.initialize()
+        try:
+            Repository(db).kv_set("preview:seeded", "1")
+        finally:
+            db.close()
+        cli._assert_preview_database(db_path)
+
+        try:
+            cli._assert_preview_database(Path(tmp) / "missing.db")
+        except cli.ConfigError as exc:
+            assert "不存在" in str(exc)
+        else:
+            raise AssertionError("缺失数据库应报错")
+
+
 def test_default_command_starts_web_and_scheduler():
     with tempfile.TemporaryDirectory() as tmp:
         path = write_config(tmp)
@@ -299,6 +327,7 @@ def main_test():
     test_auth_check_without_cookie()
     test_auth_check_all_and_auth_dispatch()
     test_run_once_offline()
+    test_serve_preview_guard()
     test_default_command_starts_web_and_scheduler()
     test_snapshot_backup_failure_returns_error_and_retries()
     test_candidates_and_discover_commands()