feat: v0.3.1 — Go/Gin 后端重写 + gh-ost 集成

架构变更:
- Python/FastAPI → Go/Gin 重写（Python 后端保留在 backend-python/）
- GORM + SQLite（兼容现有数据库表结构）
- JWT 认证 + RBAC 权限中间件

Go 后端结构:
- cmd/server/main.go — 入口，端口 9000
- config/config.go — 环境变量配置
- internal/model/ — GORM 模型（30张表，完全兼容 SQLite）
- internal/handler/ — auth/instance/ticket/dashboard/ghost handler
- internal/middleware/ — JWT 认证 + CORS
- internal/ghost/ — gh-ost 集成模块（同步/异步执行，任务管理）
- router/router.go — API 路由注册（/api/v1/...）

gh-ost 集成:
- RunGhOst() 同步执行
- RunGhOstAsync() 异步执行 + 进度追踪
- TaskManager 管理多个并发任务
- API: POST /ghost/dry-run, /ghost/execute, GET /ghost/status/:taskId

核心 API 已对齐:
- POST /auth/login (JWT)
- GET /dashboard/stats, /dashboard/my-tickets
- GET /tickets/statistics, CRUD + approve/execute
- GET/POST/PUT/DELETE /instances
- GET /users, /audit-rules, /announcements, /settings

已验证:
- 登录 admin/admin123 ✅
- Dashboard 99工单/110查询/4实例 ✅
- 工单统计按角色过滤 ✅

backend/router/router.go

@@ -0,0 +1,81 @@
+package router
+
+import (
+	"sql-platform/internal/handler"
+	"sql-platform/internal/middleware"
+
+	"github.com/gin-gonic/gin"
+)
+
+func Setup(r *gin.Engine) {
+	api := r.Group("/api/v1")
+
+	// Public routes
+	api.POST("/auth/login", handler.Login)
+
+	// Authenticated routes
+	auth := api.Group("")
+	auth.Use(middleware.AuthMiddleware())
+	{
+		// Auth
+		auth.GET("/auth/me", handler.GetMe)
+
+		// Dashboard
+		auth.GET("/dashboard/stats", handler.DashboardStats)
+		auth.GET("/dashboard/my-tickets", handler.MyTickets)
+
+		// Tickets
+		auth.GET("/tickets/statistics", handler.TicketStatistics)
+		auth.GET("/tickets", handler.ListTickets)
+		auth.GET("/tickets/:id", handler.GetTicket)
+		auth.POST("/tickets", handler.CreateTicket)
+		auth.POST("/tickets/:id/approve", handler.ApproveTicket)
+		auth.POST("/tickets/:id/execute", handler.ExecuteTicket)
+
+		// Instances
+		auth.GET("/instances", handler.ListInstances)
+		auth.GET("/instances/stats", handler.InstanceStats)
+		auth.GET("/instances/:id", handler.GetInstance)
+		auth.POST("/instances/:id/test-connection", handler.TestConnection)
+
+		// Instance management (admin/dba only)
+		admin := auth.Group("")
+		admin.Use(middleware.RequireRole("admin", "dba"))
+		{
+			admin.POST("/instances", handler.CreateInstance)
+			admin.PUT("/instances/:id", handler.UpdateInstance)
+			admin.DELETE("/instances/:id", handler.DeleteInstance)
+		}
+
+		// Users (admin only)
+		userAdmin := auth.Group("")
+		userAdmin.Use(middleware.RequireRole("admin"))
+		{
+			userAdmin.GET("/users", handler.ListUsers)
+			userAdmin.POST("/users", handler.CreateUser)
+			userAdmin.PUT("/users/:id", handler.UpdateUser)
+			userAdmin.DELETE("/users/:id", handler.DeleteUser)
+		}
+
+		// gh-ost (admin/dba only)
+		ghostGroup := auth.Group("")
+		ghostGroup.Use(middleware.RequireRole("admin", "dba"))
+		{
+			ghostGroup.POST("/ghost/dry-run", handler.GhOstDryRun)
+			ghostGroup.POST("/ghost/execute", handler.GhOstExecute)
+			ghostGroup.GET("/ghost/status/:taskId", handler.GhOstStatus)
+			ghostGroup.GET("/ghost/tasks", handler.GhOstListTasks)
+		}
+
+		// Read-only resources
+		auth.GET("/audit-rules", handler.ListAuditRules)
+		auth.GET("/announcements", handler.ListAnnouncements)
+		auth.GET("/query-histories", handler.ListQueryHistories)
+		auth.GET("/settings", handler.ListSettings)
+		auth.GET("/notifications/channels", handler.ListNotificationChannels)
+		auth.GET("/notifications/templates", handler.ListNotificationTemplates)
+		auth.GET("/workflows", handler.ListWorkflows)
+		auth.GET("/instance-groups", handler.ListInstanceGroups)
+		auth.POST("/notifications/test", handler.TestNotification)
+	}
+}