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/manifest.go

@@ -0,0 +1,22 @@
+package registry
+
+import (
+	"time"
+
+	"gorm.io/gorm"
+)
+
+// Manifest manifest ??
+type Manifest 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:"-"`
+
+	Repository string `gorm:"index;not null" json:"repository"` // ????
+	Tag         string `gorm:"index;not null" json:"tag"`        // tag ??
+	Digest      string `gorm:"uniqueIndex;not null" json:"digest"` // manifest digest
+	MediaType   string `json:"media_type"`                       // ????
+	Size        int64  `gorm:"not null" json:"size"`              // manifest ??
+	Content     []byte `gorm:"type:blob" json:"-"`                // manifest ???JSON?
+}