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/views/admin/system-settings/BasicConfigSection.vue

@@ -0,0 +1,148 @@
+<template>
+  <CardSection
+    title="基础配置"
+    description="配置系统默认参数"
+  >
+    <template #actions>
+      <Button
+        size="sm"
+        :disabled="loading || !hasChanges"
+        @click="$emit('save')"
+      >
+        {{ loading ? '保存中...' : '保存' }}
+      </Button>
+    </template>
+    <div class="grid grid-cols-1 md:grid-cols-2 gap-6">
+      <div>
+        <Label
+          for="default-quota"
+          class="block text-sm font-medium"
+        >
+          默认用户配额(美元)
+        </Label>
+        <Input
+          id="default-quota"
+          :model-value="defaultUserQuotaUsd"
+          type="number"
+          step="0.01"
+          placeholder="10.00"
+          class="mt-1"
+          @update:model-value="$emit('update:defaultUserQuotaUsd', Number($event))"
+        />
+        <p class="mt-1 text-xs text-muted-foreground">
+          新用户注册时的默认配额
+        </p>
+      </div>
+
+      <div>
+        <Label
+          for="rate-limit"
+          class="block text-sm font-medium"
+        >
+          每分钟请求限制
+        </Label>
+        <Input
+          id="rate-limit"
+          :model-value="rateLimitPerMinute"
+          type="number"
+          placeholder="0"
+          class="mt-1"
+          @update:model-value="$emit('update:rateLimitPerMinute', Number($event))"
+        />
+        <p class="mt-1 text-xs text-muted-foreground">
+          0 表示不限制
+        </p>
+      </div>
+
+      <div class="flex items-center h-full">
+        <div class="flex items-center space-x-2">
+          <Checkbox
+            id="enable-registration"
+            :checked="enableRegistration"
+            @update:checked="$emit('update:enableRegistration', $event)"
+          />
+          <div>
+            <Label
+              for="enable-registration"
+              class="cursor-pointer"
+            >
+              开放用户注册
+            </Label>
+            <p class="text-xs text-muted-foreground">
+              允许新用户自助注册账户
+            </p>
+          </div>
+        </div>
+      </div>
+
+      <div class="flex items-center h-full">
+        <div class="flex items-center space-x-2">
+          <Checkbox
+            id="auto-delete-expired-keys"
+            :checked="autoDeleteExpiredKeys"
+            @update:checked="$emit('update:autoDeleteExpiredKeys', $event)"
+          />
+          <div>
+            <Label
+              for="auto-delete-expired-keys"
+              class="cursor-pointer"
+            >
+              自动删除过期 Key
+            </Label>
+            <p class="text-xs text-muted-foreground">
+              关闭时仅禁用过期的独立余额 Key
+            </p>
+          </div>
+        </div>
+      </div>
+
+      <div class="flex items-center h-full">
+        <div class="flex items-center space-x-2">
+          <Checkbox
+            id="enable-format-conversion"
+            :checked="enableFormatConversion"
+            @update:checked="$emit('update:enableFormatConversion', $event)"
+          />
+          <div>
+            <Label
+              for="enable-format-conversion"
+              class="cursor-pointer"
+            >
+              全局格式转换
+            </Label>
+            <p class="text-xs text-muted-foreground">
+              开启后强制允许所有提供商接受跨格式请求
+            </p>
+          </div>
+        </div>
+      </div>
+    </div>
+  </CardSection>
+</template>
+
+<script setup lang="ts">
+import Button from '@/components/ui/button.vue'
+import Input from '@/components/ui/input.vue'
+import Label from '@/components/ui/label.vue'
+import Checkbox from '@/components/ui/checkbox.vue'
+import { CardSection } from '@/components/layout'
+
+defineProps<{
+  defaultUserQuotaUsd: number
+  rateLimitPerMinute: number
+  enableRegistration: boolean
+  autoDeleteExpiredKeys: boolean
+  enableFormatConversion: boolean
+  loading: boolean
+  hasChanges: boolean
+}>()
+
+defineEmits<{
+  save: []
+  'update:defaultUserQuotaUsd': [value: number]
+  'update:rateLimitPerMinute': [value: number]
+  'update:enableRegistration': [value: boolean]
+  'update:autoDeleteExpiredKeys': [value: boolean]
+  'update:enableFormatConversion': [value: boolean]
+}>()
+</script>