fix: cleanup k8s configs, add deploy.sh, remove hardcoded secrets

- Add one-click deploy script (k8s/deploy.sh) for test + prod
- Add startupProbe to backend (60x10s = 10min grace for ML model loading)
- Add configmap.yaml and secret.yaml (envsubst from backend/.env)
- Fix image URLs: add registry.plfai.cn prefix
- Fix frontend: API base URL relative (/api/v1), login-required mode
- Remove hardcoded localhost references from frontend
- Clean broken kustomize overlays
- Add nodeAffinity for backend→k8smaster, frontend→plf-cvm/k8smaster
- Remove dead ReplicaSets and stale pods during deploy

frontend/src/app/components/pages/QAChat.tsx

@@ -79,7 +79,7 @@ export function QAChat() {
       setMessages(prev => [...prev, {
         id: `err${Date.now()}`,
         role: 'ai',
-        content: `⚠️ 请求失败：${msg}\n\n请确认：\n1. 后端服务已启动（localhost:8000）\n2. 知识图谱已有数据（请先上传并索引文档）\n3. DeepSeek API Key 已配置`,
+        content: `⚠️ 请求失败：${msg}\n\n请确认：\n1. 后端服务已启动\n2. 知识图谱已有数据（请先上传并索引文档）\n3. DeepSeek API Key 已配置`,
         timestamp: new Date().toISOString(),
       }]);
     } finally {