feat(trade): implement second-hand trading/flea market feature

Add complete trade functionality including:
- TradeItem, TradeImage, TradeFavorite models with auto-migration
- TradeRepository with CRUD and favorite operations
- TradeService with business logic for listing, creating, updating, status management
- TradeHandler with RESTful endpoints for trade operations
- DTOs and converters for request/response handling

Routes include: list, get by id, create, update, delete, status update, view recording, favorite/unfavorite.

internal/router/router.go

@@ -43,6 +43,7 @@ type Router struct {
 	adminVerificationHandler *handler.AdminVerificationHandler
 	adminProfileAuditHandler *handler.AdminProfileAuditHandler
 	setupHandler            *handler.SetupHandler
+	tradeHandler            *handler.TradeHandler
 	wsHandler                *handler.WSHandler
 	logService               *service.LogService
 	jwtService               *service.JWTService
@@ -81,8 +82,9 @@ func New(
 	verificationHandler *handler.VerificationHandler,
 	adminVerificationHandler *handler.AdminVerificationHandler,
 	adminProfileAuditHandler *handler.AdminProfileAuditHandler,
-	setupHandler *handler.SetupHandler,
-	logService *service.LogService,
+	setupHandler            *handler.SetupHandler,
+	tradeHandler            *handler.TradeHandler,
+	logService               *service.LogService,
 	activityService service.UserActivityService,
 	casbinService service.CasbinService,
 	wsHandler *handler.WSHandler,
@@ -124,6 +126,7 @@ func New(
 		adminVerificationHandler: adminVerificationHandler,
 		adminProfileAuditHandler: adminProfileAuditHandler,
 		setupHandler:             setupHandler,
+		tradeHandler:             tradeHandler,
 		logService:               logService,
 		jwtService:               jwtService,
 		casbinService:            casbinService,
@@ -311,6 +314,22 @@ func (r *Router) setupRoutes() {
 			}
 		}
 
+		// 二手交易路由
+		if r.tradeHandler != nil {
+			trade := v1.Group("/trade")
+			{
+				trade.GET("", middleware.OptionalAuth(r.jwtService), r.tradeHandler.List)
+				trade.GET("/:id", middleware.OptionalAuth(r.jwtService), r.tradeHandler.GetByID)
+				trade.POST("", authMiddleware, middleware.RequireVerified(r.userRepo), r.tradeHandler.Create)
+				trade.PUT("/:id", authMiddleware, middleware.RequireVerified(r.userRepo), r.tradeHandler.Update)
+				trade.DELETE("/:id", authMiddleware, middleware.RequireVerified(r.userRepo), r.tradeHandler.Delete)
+				trade.PUT("/:id/status", authMiddleware, middleware.RequireVerified(r.userRepo), r.tradeHandler.UpdateStatus)
+				trade.POST("/:id/view", middleware.OptionalAuth(r.jwtService), r.tradeHandler.RecordView)
+				trade.POST("/:id/favorite", authMiddleware, middleware.RequireVerified(r.userRepo), r.tradeHandler.Favorite)
+				trade.DELETE("/:id/favorite", authMiddleware, middleware.RequireVerified(r.userRepo), r.tradeHandler.Unfavorite)
+			}
+		}
+
 		// 课表路由
 		if r.scheduleHandler != nil {
 			schedule := v1.Group("/schedule")