docs(swagger): fix response type annotations for swagger generation

Update DeleteMasterKey endpoint to use MapData instead of dto.DeleteResponse
and add blank references for model registry DTOs to ensure proper swagger
documentation generation.

internal/api/admin_handler.go

@@ -523,7 +523,7 @@ func (h *AdminHandler) ListKeysForMaster(c *gin.Context) {
 // @Security     AdminAuth
 // @Param        id      path  int  true  "Master ID"
 // @Param        key_id  path  int  true  "Token ID"
-// @Success      200  {object}  ResponseEnvelope{data=dto.DeleteResponse}
+// @Success      200  {object}  ResponseEnvelope{data=MapData}
 // @Failure      400  {object}  ResponseEnvelope{data=MapData}
 // @Failure      404  {object}  ResponseEnvelope{data=MapData}
 // @Failure      500  {object}  ResponseEnvelope{data=MapData}

internal/api/model_registry_handler.go

@@ -4,10 +4,17 @@ import (
 	"net/http"
 	"strings"
 
+	"github.com/ez-api/ez-api/internal/dto"
 	"github.com/ez-api/ez-api/internal/service"
 	"github.com/gin-gonic/gin"
 )
 
+// Blank references for swagger doc generation
+var (
+	_ dto.ModelRegistryStatusResponse
+	_ dto.ModelRegistryCheckResponse
+)
+
 type ModelRegistryHandler struct {
 	reg *service.ModelRegistryService
 }