feat: 品牌重命名 Sub2API -> TianShuAPI

- 前端: 所有界面显示、i18n 文本、组件中的品牌名称
- 后端: 服务层、设置默认值、邮件模板、安装向导
- 数据库: 迁移脚本注释
- 保持功能完全一致，仅更改品牌名称

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

backend/internal/handler/handler.go

@@ -1,44 +1,44 @@
-package handler
-
-import (
-	"github.com/Wei-Shaw/sub2api/internal/handler/admin"
-)
-
-// AdminHandlers contains all admin-related HTTP handlers
-type AdminHandlers struct {
-	Dashboard        *admin.DashboardHandler
-	User             *admin.UserHandler
-	Group            *admin.GroupHandler
-	Account          *admin.AccountHandler
-	OAuth            *admin.OAuthHandler
-	OpenAIOAuth      *admin.OpenAIOAuthHandler
-	GeminiOAuth      *admin.GeminiOAuthHandler
-	AntigravityOAuth *admin.AntigravityOAuthHandler
-	Proxy            *admin.ProxyHandler
-	Redeem           *admin.RedeemHandler
-	Setting          *admin.SettingHandler
-	System           *admin.SystemHandler
-	Subscription     *admin.SubscriptionHandler
-	Usage            *admin.UsageHandler
-	UserAttribute    *admin.UserAttributeHandler
-}
-
-// Handlers contains all HTTP handlers
-type Handlers struct {
-	Auth          *AuthHandler
-	User          *UserHandler
-	APIKey        *APIKeyHandler
-	Usage         *UsageHandler
-	Redeem        *RedeemHandler
-	Subscription  *SubscriptionHandler
-	Admin         *AdminHandlers
-	Gateway       *GatewayHandler
-	OpenAIGateway *OpenAIGatewayHandler
-	Setting       *SettingHandler
-}
-
-// BuildInfo contains build-time information
-type BuildInfo struct {
-	Version   string
-	BuildType string // "source" for manual builds, "release" for CI builds
-}
+package handler
+
+import (
+	"github.com/Wei-Shaw/sub2api/internal/handler/admin"
+)
+
+// AdminHandlers contains all admin-related HTTP handlers
+type AdminHandlers struct {
+	Dashboard        *admin.DashboardHandler
+	User             *admin.UserHandler
+	Group            *admin.GroupHandler
+	Account          *admin.AccountHandler
+	OAuth            *admin.OAuthHandler
+	OpenAIOAuth      *admin.OpenAIOAuthHandler
+	GeminiOAuth      *admin.GeminiOAuthHandler
+	AntigravityOAuth *admin.AntigravityOAuthHandler
+	Proxy            *admin.ProxyHandler
+	Redeem           *admin.RedeemHandler
+	Setting          *admin.SettingHandler
+	System           *admin.SystemHandler
+	Subscription     *admin.SubscriptionHandler
+	Usage            *admin.UsageHandler
+	UserAttribute    *admin.UserAttributeHandler
+}
+
+// Handlers contains all HTTP handlers
+type Handlers struct {
+	Auth          *AuthHandler
+	User          *UserHandler
+	APIKey        *APIKeyHandler
+	Usage         *UsageHandler
+	Redeem        *RedeemHandler
+	Subscription  *SubscriptionHandler
+	Admin         *AdminHandlers
+	Gateway       *GatewayHandler
+	OpenAIGateway *OpenAIGatewayHandler
+	Setting       *SettingHandler
+}
+
+// BuildInfo contains build-time information
+type BuildInfo struct {
+	Version   string
+	BuildType string // "source" for manual builds, "release" for CI builds
+}