feat(failover): 支持 Provider 级别故障转移规则，默认全部转移策略

- 新增 failover_rules 配置：支持 success_failover_patterns（成功响应匹配时转移）
  和 error_stop_patterns（错误响应匹配时终止），支持按 status_code 过滤
- 修改默认转移策略：ErrorClassifier 不再返回 RAISE，所有错误默认继续转移
- TaskService 中客户端错误不再直接抛出，改为 break 继续尝试下一个候选
- 修复 proxy tunnel 连接/断连竞态：引入 per-node 锁和事件时间戳排序
- 优化 ProxyNode 状态判定：OFFLINE 统一由心跳超时判定，兼容多 worker 场景
- has_tunnel 改为纯检查方法，避免在 finally 块中误清理新注册连接
- Redis stream NOGROUP 异常自愈处理
- OAuthAccountDialog 输入框焦点样式补全

frontend/src/features/providers/components/OAuthAccountDialog.vue

@@ -138,7 +138,7 @@
                       v-model="device.start_url"
                       type="text"
                       placeholder="https://your-org.awsapps.com/start"
-                      class="w-full h-8 px-2 text-xs rounded-md border border-border bg-background font-mono"
+                      class="w-full h-8 px-2 text-xs rounded-md border border-border bg-background font-mono focus:outline-none focus:ring-1 focus:ring-ring focus:relative focus:z-10"
                       spellcheck="false"
                     >
                   </div>
@@ -154,7 +154,7 @@
                         <ComboboxInput
                           :display-value="() => device.region"
                           placeholder="输入或选择 Region"
-                          class="w-full h-8 px-2 pr-7 text-xs rounded-md border border-border bg-background font-mono focus:outline-none focus:ring-1 focus:ring-ring"
+                          class="w-full h-8 px-2 pr-7 text-xs rounded-md border border-border bg-background font-mono focus:outline-none focus:ring-1 focus:ring-ring focus:relative focus:z-10"
                           spellcheck="false"
                           @input="(e: Event) => regionSearch = (e.target as HTMLInputElement).value"
                           @keydown.enter.prevent="onRegionEnter"
@@ -193,7 +193,7 @@
                       v-model="device.totp_secret"
                       type="text"
                       placeholder="Base32 secret, 如 JBSWY3DPEHPK3PXP"
-                      class="w-full h-8 px-2 text-xs rounded-md border border-border bg-background font-mono"
+                      class="w-full h-8 px-2 text-xs rounded-md border border-border bg-background font-mono focus:outline-none focus:ring-1 focus:ring-ring focus:relative focus:z-10"
                       spellcheck="false"
                     >
                   </div>