fix(mcp/k8s): _kubectl_scale 補 validate_deployment_exists dry-run

根因：_kubectl_restart 有 dry-run 驗證，_kubectl_scale 完全沒有
     → gitea（docker-compose，不在 K8s）直接被 kubectl scale 執行
     → Deployment 'gitea' not found in namespace 'awoooi-prod'（INC-20260425-3B6C39）

修復：_kubectl_scale 在執行前加 validate_deployment_exists，
     K8s 找不到 deployment 時返回 error 而非繼續執行

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

apps/api/src/plugins/mcp/providers/k8s_provider.py

@@ -336,6 +336,13 @@ class K8sProvider(MCPToolProvider):
         if not deployment:
             return {"error": "Missing 'deployment' parameter"}
 
+        # 2026-04-27 ogt + Claude Sonnet 4.6: 補 dry-run 驗證，與 _kubectl_restart 對齊
+        # 根因：_kubectl_scale 缺 validate_deployment_exists → gitea（docker-compose 服務）
+        #       直接被 kubectl scale → K8s not found 執行失敗（INC-20260425-3B6C39 事故）
+        dry_run = await executor.validate_deployment_exists(deployment, namespace)
+        if not dry_run.passed:
+            return {"error": dry_run.message, "dry_run": False}
+
         cmd = f"kubectl scale deployment/{deployment} --replicas={replicas} -n {namespace}"
         result = await executor.execute_kubectl_command(cmd)