security: Sentinel 配置文件模板化 — config.yaml 不入库

- config.yaml → .gitignore (含 API Key 不入库)
- config.yaml.example 模板 (空节点列表)
- 首次启动自动从模板复制
- 所有插件 config.yaml 统一保护

Co-Authored-By: Claude <noreply@anthropic.com>

plugins/sentinel/__init__.py

@@ -77,6 +77,15 @@ class Plugin(PluginWebMixin):
         try:
             with open(self._config_path, "r") as f:
                 return yaml.safe_load(f) or {}
+        except FileNotFoundError:
+            # 从模板创建
+            template = self._config_path + ".example"
+            if os.path.exists(template):
+                import shutil
+                shutil.copy(template, self._config_path)
+                with open(self._config_path, "r") as f:
+                    return yaml.safe_load(f) or {}
+            return {}
         except Exception:
             return {}