fix(api): 修復 MCP providers lint 錯誤

- interfaces.py: 修正 import 排序
- signoz_provider.py: 移除未使用變數

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

apps/api/src/plugins/mcp/interfaces.py

@@ -17,7 +17,6 @@ from typing import Any
 
 from src.utils.timezone import now_taipei
 
-
 # =============================================================================
 # Data Classes (DTO)
 # =============================================================================

apps/api/src/plugins/mcp/providers/signoz_provider.py

@@ -187,8 +187,8 @@ class SignOzProvider(MCPToolProvider):
     async def health_check(self) -> bool:
         """Check if SignOz is accessible"""
         try:
-            client = self._get_client()
-            # Try to get metrics for a test service
-            return True  # SignOz client initialization is the check
+            # SignOz client initialization is the health check
+            self._get_client()
+            return True
         except Exception:
             return False