feat: Sentinel 支持自定义 API 路径前缀 (base_path)

- 节点编辑对话框新增「API 路径前缀」字段 (默认 /SenSu)
- 后端保存/读取 base_path
- API 响应包含 base_path 供前端回显

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

plugins/sentinel/__init__.py

@@ -109,6 +109,7 @@ class Plugin(PluginWebMixin):
             result.append({
                 "id": n.get("id", ""), "name": n.get("name", ""), "url": n.get("url", ""),
                 "notes": n.get("notes", ""),
+                "base_path": n.get("base_path", "/SenSu"),
                 "enabled": n.get("enabled", True),
                 "online": c.get("online", False),
                 "system": c.get("system", {}),
@@ -130,6 +131,7 @@ class Plugin(PluginWebMixin):
                 "name": data.get("name", "").strip(),
                 "url": data.get("url", "").strip().rstrip("/"),
                 "api_key": data.get("api_key", "").strip(),
+                "base_path": data.get("base_path", "/SenSu").strip() or "/SenSu",
                 "notes": data.get("notes", "").strip(),
                 "enabled": data.get("enabled", True),
             }
@@ -233,6 +235,7 @@ class Plugin(PluginWebMixin):
             result.append({
                 "id": n.get("id", ""), "name": n.get("name", ""), "url": n.get("url", ""),
                 "notes": n.get("notes", ""),
+                "base_path": n.get("base_path", "/SenSu"),
                 "enabled": n.get("enabled", True),
                 "online": c.get("online", False),
                 "system": c.get("system", {}),