feat: Agent批量升级 + 版本号注入 + 服务器凭证下拉关联

- Dockerfile: ARG VERSION/BUILD_TIME 通过 ldflags 注入 agent+backend 二进制
- run.sh: 自动从 git tag 获取版本号
- docker-compose: build args 传递 VERSION/BUILD_TIME
- backend: BatchUpgradeAgent SSH下载新二进制+重启, /agent/bin 静态文件服务
- frontend: 监控大屏添加批量升级按钮 (闪电图标)
- frontend: 服务器编辑/添加表单改为凭证下拉选择器
- frontend: ServerForm 加载 /credentials 列表, 选择后自动填充用户名/认证方式

frontend/src/services/api.ts

@@ -505,6 +505,7 @@ export const agentApi = {
   // Agent 安装/卸载
   uninstallAgent: (data: { hostname?: string; server_id?: number }) => http.post('/agent/uninstall', data),
   batchUninstall: (serverIds: number[]) => http.post('/agent/batch-uninstall', { server_ids: serverIds }),
+  batchUpgrade: (serverIds: number[]) => http.post('/agent/batch-upgrade', { server_ids: serverIds }),
   listAlerts: (params?: Record<string, string>) => http.get('/agent/alerts', params),
   resolveAlert: (id: number) => http.post(`/agent/alerts/${id}/resolve`),
 };