refactor: 继续拆分大型模块并增强模块注册健壮性

后端:
- chat_handler_base 错误处理函数提取到 chat_error_utils 子模块
- CLI mixin 引入 CliHandlerProtocol 协议类改善类型标注
- aware_scheduler 拆分为 _candidate_builder 和 _candidate_sorter 子模块
- usage recording 拆分为 _billing_integration 和 _recording_helpers 子模块
- ModuleRegistry 添加循环依赖检测，将写操作从查询方法分离到 reconcile_module_state
- 修正 plugin manager 入度注释

前端:
- 路由守卫逻辑拆分为独立 guards 模块
- ProviderManagement 拆分为 TableHeader/TableRow/BalanceCell/MobileCard 子组件
- SystemSettings 拆分为多个 Section 子组件和 composables
- 提取 useEndpointStatus/useProviderBalance/useProviderFilters composables

测试适配重构后的子模块结构

frontend/src/features/providers/composables/useEndpointStatus.ts

@@ -0,0 +1,90 @@
+import type { EndpointHealthDetail } from '@/api/endpoints'
+
+// 端点状态枚举
+export type EndpointStatus = 'disabled' | 'no_keys' | 'keys_disabled' | 'available'
+
+const ENDPOINT_SORT_ORDER = [
+  'claude:chat',
+  'claude:cli',
+  'openai:chat',
+  'openai:cli',
+  'gemini:chat',
+  'gemini:cli',
+  'openai:video',
+  'gemini:video',
+]
+
+/**
+ * 端点排序
+ */
+export function sortEndpoints<T extends { api_format: string }>(endpoints: T[]): T[] {
+  return [...endpoints].sort((a, b) => {
+    return ENDPOINT_SORT_ORDER.indexOf(a.api_format) - ENDPOINT_SORT_ORDER.indexOf(b.api_format)
+  })
+}
+
+/**
+ * 获取端点状态
+ */
+export function getEndpointStatus(endpoint: EndpointHealthDetail): EndpointStatus {
+  if (endpoint.is_active === false) {
+    return 'disabled'
+  }
+  if ((endpoint.active_keys ?? 0) === 0) {
+    return (endpoint.total_keys ?? 0) > 0 ? 'keys_disabled' : 'no_keys'
+  }
+  return 'available'
+}
+
+/**
+ * 判断端点是否可用
+ */
+export function isEndpointAvailable(endpoint: EndpointHealthDetail): boolean {
+  return getEndpointStatus(endpoint) === 'available'
+}
+
+/**
+ * 根据健康分数获取颜色
+ */
+export function getHealthScoreColor(score: number | undefined | null): string {
+  if (score === undefined || score === null) {
+    return 'bg-muted-foreground/40'
+  }
+  if (score >= 0.8) return 'bg-green-500'
+  if (score >= 0.5) return 'bg-amber-500'
+  return 'bg-red-500'
+}
+
+/**
+ * 端点不可用时进度条颜色
+ */
+export function getEndpointDotColor(endpoint: EndpointHealthDetail): string {
+  if (!isEndpointAvailable(endpoint)) {
+    return 'bg-muted-foreground/40'
+  }
+  return getHealthScoreColor(endpoint.health_score)
+}
+
+/**
+ * 端点提示文本
+ */
+export function getEndpointTooltip(endpoint: EndpointHealthDetail): string {
+  const format = endpoint.api_format
+  const status = getEndpointStatus(endpoint)
+
+  switch (status) {
+    case 'disabled':
+      return `${format}: 端点已禁用`
+    case 'no_keys':
+      return `${format}: 未配置密钥`
+    case 'keys_disabled':
+      return `${format}: 无可用密钥`
+    case 'available': {
+      const score = endpoint.health_score
+      if (score === undefined || score === null) {
+        return `${format}: 暂无健康数据`
+      }
+      return `${format}: 健康度 ${(score * 100).toFixed(0)}%`
+    }
+  }
+}