refactor(architecture): eliminate internal package and complete cordis single-owner model and repository migration

- Physically purged all legacy internal/ packages, centralized pkg/model/ and pkg/repository/
- Migrated domain models and database repositories into self-contained owner plugins (user, auth, message_gateway, admin, upload, risk_control)
- Decoupled cross-plugin interactions via pure core/contracts and typed EventBus
- Ensured 100% test coverage pass, zero data races (-race clean), and 0 lint issues in make code-check

plugins/domain/message_gateway/push_channels.go

@@ -11,9 +11,8 @@ import (
 	"strings"
 	"sync"
 
-	"github.com/Rain-kl/Wavelet/internal/model"
-	"github.com/Rain-kl/Wavelet/internal/shared/response"
 	pkgpush "github.com/Rain-kl/Wavelet/pkg/push"
+	"github.com/Rain-kl/Wavelet/pkg/response"
 	"github.com/gin-gonic/gin"
 	"gorm.io/gorm"
 )
@@ -314,7 +313,7 @@ func TestPushChannel(c *gin.Context) {
 		url, token, other = resolveSMTPConfig(ctx, url, token, other)
 	}
 
-	tempChannel := model.PushChannel{
+	tempChannel := PushChannel{
 		Name:    "test_temp",
 		URL:     url,
 		Token:   token,