refactor: 拆分职责、引入 dataclass 封装并增强缓存健壮性

- ErrorClassifier 副作用操作分离为 ErrorHandlerService（缓存失效、健康记录、RPM 调整）
- chat_handler_base 提取 ProviderRequestResult dataclass 和 _prepare_provider_request 方法
- failover 提取 AttemptErrorOutcome dataclass 和辅助方法
- formula_engine 拆分 _resolve_mapping 为子方法，增加求值异常日志
- usage recording 引入 UsageCostInfo dataclass 封装成本参数
- 前端 types.ts 拆分为 types/ 子模块
- cache backend 工厂函数加锁防止并发重复创建，LocalCache 容量检查修正
- CacheSync 监听增加断线重连机制，publish 增加重试
- guide 页面修正 useSiteInfo() 调用顺序

frontend/src/views/public/guide/AdvancedGuide.vue

@@ -4,8 +4,6 @@ import { ArrowRight, Shuffle, FileCode, Globe, Shield, Check, Info, AlertTriangl
 import { panelClasses } from './guide-config'
 import { useSiteInfo } from '@/composables/useSiteInfo'
 
-const { siteName } = useSiteInfo()
-
 withDefaults(
   defineProps<{
     baseUrl?: string
@@ -15,6 +13,8 @@ withDefaults(
   }
 )
 
+const { siteName } = useSiteInfo()
+
 // 格式转换示例
 const conversionExamples = [
   {

frontend/src/views/public/guide/GuideFaq.vue

@@ -4,8 +4,6 @@ import { Search, ChevronDown, ExternalLink, HelpCircle } from 'lucide-vue-next'
 import { faqItems, panelClasses } from './guide-config'
 import { useSiteInfo } from '@/composables/useSiteInfo'
 
-const { siteName } = useSiteInfo()
-
 withDefaults(
   defineProps<{
     baseUrl?: string
@@ -15,6 +13,8 @@ withDefaults(
   }
 )
 
+const { siteName } = useSiteInfo()
+
 // 搜索关键词
 const searchQuery = ref('')
 

frontend/src/views/public/guide/Overview.vue

@@ -4,8 +4,6 @@ import { ArrowRight, Server, Layers, Key, Box, ChevronRight } from 'lucide-vue-n
 import { coreConcepts, apiFormats, configSteps, panelClasses } from './guide-config'
 import { useSiteInfo } from '@/composables/useSiteInfo'
 
-const { siteName } = useSiteInfo()
-
 withDefaults(
   defineProps<{
     baseUrl?: string
@@ -15,6 +13,8 @@ withDefaults(
   }
 )
 
+const { siteName } = useSiteInfo()
+
 // 概念图标映射
 const conceptIcons = {
   blue: Server,

frontend/src/views/public/guide/ProviderGuide.vue

@@ -4,8 +4,6 @@ import { ArrowRight, Server, Settings, Check, AlertTriangle, Info } from 'lucide
 import { apiFormats, panelClasses } from './guide-config'
 import { useSiteInfo } from '@/composables/useSiteInfo'
 
-const { siteName } = useSiteInfo()
-
 withDefaults(
   defineProps<{
     baseUrl?: string
@@ -15,6 +13,8 @@ withDefaults(
   }
 )
 
+const { siteName } = useSiteInfo()
+
 // 端点配置字段说明
 const endpointFields = [
   { name: '名称', description: '端点的显示名称，用于区分不同的端点', required: true },

frontend/src/views/public/guide/UserKeyGuide.vue

@@ -4,8 +4,6 @@ import { ArrowRight, Users, Key, Shield, Check, Info, AlertTriangle, Clock } fro
 import { panelClasses } from './guide-config'
 import { useSiteInfo } from '@/composables/useSiteInfo'
 
-const { siteName } = useSiteInfo()
-
 withDefaults(
   defineProps<{
     baseUrl?: string
@@ -15,6 +13,8 @@ withDefaults(
   }
 )
 
+const { siteName } = useSiteInfo()
+
 // API Key 字段说明
 const keyFields = [
   { name: '名称', description: 'Key 的描述性名称，方便识别', required: true },