refactor: reorganize models to pkg/model and add authentication module

- Move ORM models from internal/model to pkg/model organized by module (auth/k8s/registry)
- Add authentication module with login, user management handlers
- Update all import paths to use new model locations
- Add frontend auth pages (Login, UserManagement) and authStore
- Remove deprecated internal/model/model.go

pkg/model/registry/blob.go

@@ -0,0 +1,20 @@
+package registry
+
+import (
+	"time"
+
+	"gorm.io/gorm"
+)
+
+// Blob blob ??
+type Blob struct {
+	ID        uint           `gorm:"primarykey" json:"id"`
+	CreatedAt time.Time      `json:"created_at"`
+	UpdatedAt time.Time      `json:"updated_at"`
+	DeletedAt gorm.DeletedAt `gorm:"index" json:"-"`
+
+	Digest     string `gorm:"uniqueIndex;not null" json:"digest"`      // SHA256 digest
+	Size       int64  `gorm:"not null" json:"size"`                     // ??????
+	MediaType  string `json:"media_type"`                              // ????
+	Repository string `gorm:"index" json:"repository"`                 // ???????????????
+}