feat: 宿主机 ↔ 容器路径双向映射

config.yaml 新增 path_mapping 段声明宿主机前缀与容器挂载点前缀的对应关系。
用户在 Web 界面和 config 里填宿主机真实路径（如群晖 /volume2/...），
程序在真正落盘、调用云盘 SDK 前透明转成容器内路径，保证文件写到 bind mount
而不是容器 overlay 文件系统；前端显示/返回的路径再反向转回宿主机形式。

无映射配置时所有 to_container/to_host 均原样返回，向后兼容老配置。

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

module/app.py

@@ -15,6 +15,7 @@ from ruamel import yaml
 from module.cloud_drive import CloudDrive, CloudDriveConfig
 from module.filter import Filter
 from module.language import Language, set_language
+from module import path_mapper
 from utils.format import replace_date_time, validate_title
 from utils.meta_data import MetaData
 
@@ -433,6 +434,9 @@ class Application:
         """
         # pylint: disable = R0912
         # TODO: judge the storage if enough,and provide more path
+        # 先加载 path_mapping，后续 save_path / cloud_drive 路径都按此映射表解析
+        path_mapper.load_mappings(_config.get("path_mapping", []))
+
         if _config.get("save_path") is not None:
             self.save_path = _config["save_path"]
 
@@ -676,10 +680,12 @@ class Application:
             return False
 
         ret: bool = False
+        # 云盘上传也走容器路径，避免 SDK 在容器内找不到宿主机路径
+        save_path_container = path_mapper.to_container(self.save_path)
         if self.cloud_drive_config.upload_adapter == "rclone":
             ret = await CloudDrive.rclone_upload_file(
                 self.cloud_drive_config,
-                self.save_path,
+                save_path_container,
                 local_file_path,
                 progress_callback,
                 progress_args,
@@ -688,7 +694,7 @@ class Application:
             ret = await self.loop.run_in_executor(
                 self.executor,
                 CloudDrive.aligo_upload_file(
-                    self.cloud_drive_config, self.save_path, local_file_path
+                    self.cloud_drive_config, save_path_container, local_file_path
                 ),
             )
 
@@ -724,7 +730,8 @@ class Application:
                 res = os.path.join(res, media_datetime)
             elif prefix == "media_type":
                 res = os.path.join(res, media_type)
-        return res
+        # 真正落盘前把宿主机路径转成容器内挂载点路径，保证写到 bind mount 卷
+        return path_mapper.to_container(res)
 
     def get_file_name(
         self, message_id: int, file_name: Optional[str], caption: Optional[str]