修复 LLM Provider 配置热更新问题

问题：在 /admin/llm/api 页面修改 AI 提供商配置后，配置没有立即生效，AI 依然使用旧的提供商工作

根本原因：
- LLM Provider 配置在程序启动时加载到内存 (llm.State)
- 管理后台修改配置时，只更新了数据库，内存配置未更新
- AI 继续使用内存中的旧配置

解决方案：
1. 为 llm.State 添加动态更新方法 (UpdateProvider/AddProvider/RemoveProvider)
2. 在 AI Service 中暴露配置更新接口，支持运行时重新加载
3. 在配置保存后自动触发内存配置重新加载
4. 创建新的 LLM Client 使新配置立即生效

关键特性：
- 线程安全：使用 sync.RWMutex 保护并发访问
- 容错处理：重新加载失败不影响数据库更新
- 无需重启：配置修改后立即生效
- 完整测试：添加单元测试验证功能

修改文件：
- internal/llm/state.go: 添加配置更新方法
- internal/ai/service.go: 添加配置重新加载接口
- internal/llmadmin/admin_llm_routes.go: 配置更新时触发重新加载
- internal/web/web.go: 传递 AI Service 到路由
- main.go: 连接组件
- internal/llm/state_test.go: 新增单元测试
- internal/web/map_tile_proxy_routes_test.go: 修复测试

测试：
- ✅ 所有现有测试通过
- ✅ 新增测试覆盖核心功能
- ✅ 项目成功编译

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

internal/llmadmin/admin_llm_routes.go

@@ -13,7 +13,14 @@ import (
 	"meshtastic_mqtt_server/internal/webutil"
 )
 
-func RegisterRoutes(r *gin.RouterGroup, store *storepkg.Store) {
+// LLMProviderReloader is the interface for reloading LLM provider configuration
+type LLMProviderReloader interface {
+	ReloadLLMProvider(config interface{}) error
+	AddLLMProvider(config interface{}) error
+	RemoveLLMProvider(name string) error
+}
+
+func RegisterRoutes(r *gin.RouterGroup, store *storepkg.Store, aiService LLMProviderReloader) {
 	group := r.Group("/llm")
 	{
 		// LLM Message Queue
@@ -27,9 +34,9 @@ func RegisterRoutes(r *gin.RouterGroup, store *storepkg.Store) {
 		// LLM Providers
 		group.GET("/providers", handleListLLMProviders(store))
 		group.GET("/providers/:name", handleGetLLMProvider(store))
-		group.POST("/providers", handleCreateLLMProvider(store))
-		group.PUT("/providers/:name", handleUpdateLLMProvider(store))
-		group.DELETE("/providers/:name", handleDeleteLLMProvider(store))
+		group.POST("/providers", handleCreateLLMProvider(store, aiService))
+		group.PUT("/providers/:name", handleUpdateLLMProvider(store, aiService))
+		group.DELETE("/providers/:name", handleDeleteLLMProvider(store, aiService))
 
 		// LLM Tool Router
 		group.GET("/tool-router", handleGetLLMToolRouter(store))
@@ -254,7 +261,7 @@ func handleGetLLMProvider(store *storepkg.Store) gin.HandlerFunc {
 	}
 }
 
-func handleCreateLLMProvider(store *storepkg.Store) gin.HandlerFunc {
+func handleCreateLLMProvider(store *storepkg.Store, aiService LLMProviderReloader) gin.HandlerFunc {
 	return func(c *gin.Context) {
 		var req struct {
 			Name               string `json:"name"`
@@ -290,11 +297,33 @@ func handleCreateLLMProvider(store *storepkg.Store) gin.HandlerFunc {
 			return
 		}
 
+		// Reload AI service with new provider
+		if aiService != nil {
+			providerConfig := map[string]interface{}{
+				"Name":                record.Name,
+				"Active":              record.Active,
+				"APIKey":              record.APIKey,
+				"BaseURL":             record.BaseURL,
+				"Model":               record.Model,
+				"Timeout":             record.Timeout,
+				"ContextWindowTokens": record.ContextWindowTokens,
+			}
+			if err := aiService.AddLLMProvider(providerConfig); err != nil {
+				// Log warning but don't fail the request - database is already updated
+				c.JSON(http.StatusOK, gin.H{
+					"status":  "ok",
+					"item":    llmProviderDTO(*record),
+					"warning": "provider created but failed to reload AI service: " + err.Error(),
+				})
+				return
+			}
+		}
+
 		c.JSON(http.StatusOK, gin.H{"status": "ok", "item": llmProviderDTO(*record)})
 	}
 }
 
-func handleUpdateLLMProvider(store *storepkg.Store) gin.HandlerFunc {
+func handleUpdateLLMProvider(store *storepkg.Store, aiService LLMProviderReloader) gin.HandlerFunc {
 	return func(c *gin.Context) {
 		name := c.Param("name")
 		if name == "" {
@@ -355,11 +384,33 @@ func handleUpdateLLMProvider(store *storepkg.Store) gin.HandlerFunc {
 			return
 		}
 
+		// Reload AI service with updated provider
+		if aiService != nil {
+			providerConfig := map[string]interface{}{
+				"Name":                record.Name,
+				"Active":              record.Active,
+				"APIKey":              record.APIKey,
+				"BaseURL":             record.BaseURL,
+				"Model":               record.Model,
+				"Timeout":             record.Timeout,
+				"ContextWindowTokens": record.ContextWindowTokens,
+			}
+			if err := aiService.ReloadLLMProvider(providerConfig); err != nil {
+				// Log warning but don't fail the request - database is already updated
+				c.JSON(http.StatusOK, gin.H{
+					"status":  "ok",
+					"item":    llmProviderDTO(*record),
+					"warning": "provider updated but failed to reload AI service: " + err.Error(),
+				})
+				return
+			}
+		}
+
 		c.JSON(http.StatusOK, gin.H{"status": "ok", "item": llmProviderDTO(*record)})
 	}
 }
 
-func handleDeleteLLMProvider(store *storepkg.Store) gin.HandlerFunc {
+func handleDeleteLLMProvider(store *storepkg.Store, aiService LLMProviderReloader) gin.HandlerFunc {
 	return func(c *gin.Context) {
 		name := c.Param("name")
 		if name == "" {
@@ -372,6 +423,18 @@ func handleDeleteLLMProvider(store *storepkg.Store) gin.HandlerFunc {
 			return
 		}
 
+		// Remove provider from AI service
+		if aiService != nil {
+			if err := aiService.RemoveLLMProvider(name); err != nil {
+				// Log warning but don't fail the request - database is already updated
+				c.JSON(http.StatusOK, gin.H{
+					"status":  "ok",
+					"warning": "provider deleted but failed to reload AI service: " + err.Error(),
+				})
+				return
+			}
+		}
+
 		c.JSON(http.StatusOK, gin.H{"status": "ok"})
 	}
 }