feat(marketing): user profile update, ad placement management, logo limits

- Add PUT /auth/profile endpoint for nickname and avatar updates
- Add ad_placements table and CRUD admin API for managing ad units
- Add GET /marketing/ad-config public API for mini-program to fetch ad config
- Reduce logo limit from 10 to 3 per user, add 2MB file size validation

Made-with: Cursor

internal/marketing/handler/user_logo_handler.go

@@ -42,7 +42,7 @@ func (h *UserLogoHandler) Save(c *gin.Context) {
 
 	logo, err := h.svc.Save(user.ID, req)
 	if err != nil {
-		if errors.Is(err, service.ErrLogoLimitReached) {
+		if errors.Is(err, service.ErrLogoLimitReached) || errors.Is(err, service.ErrLogoTooLarge) {
 			c.JSON(http.StatusBadRequest, model.Error(http.StatusBadRequest, err.Error()))
 			return
 		}