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/auth/audit.go

@@ -8,13 +8,13 @@ import (
 	"context"
 	"encoding/json"
 
-	"github.com/Rain-kl/Wavelet/internal/model"
+	"github.com/Rain-kl/Wavelet/core/contracts"
 	"github.com/Rain-kl/Wavelet/pkg/logger"
 	"github.com/gin-gonic/gin"
 )
 
 // LogForAudit 将登录鉴权审计日志写入 Logger
-func LogForAudit(ctx context.Context, user *model.User, c *gin.Context) {
+func LogForAudit(ctx context.Context, user *contracts.UserDTO, c *gin.Context) {
 	if user == nil || c == nil {
 		return
 	}