feat: add file deduplication and hash checking for uploads

- Implemented SHA-256 hashing for uploaded files to enable deduplication.
- Added CheckHash method to verify if a file with the same hash already exists.
- Updated Upload method to reuse existing media assets if a duplicate is found.
- Introduced a new hash column in the media_assets table to store file hashes.
- Enhanced the upload process to include progress tracking and hash calculation.
- Modified frontend to check for existing files before uploading and to show upload progress.
- Added vuedraggable for drag-and-drop functionality in the content editing view.

backend/database/models/contents.gen.go

@@ -39,9 +39,9 @@ type Content struct {
 	UpdatedAt           time.Time                `gorm:"column:updated_at;type:timestamp with time zone;default:now()" json:"updated_at"`
 	DeletedAt           gorm.DeletedAt           `gorm:"column:deleted_at;type:timestamp with time zone" json:"deleted_at"`
 	Key                 string                   `gorm:"column:key;type:character varying(32);comment:Musical key/tone" json:"key"` // Musical key/tone
-	Author              *User                    `gorm:"foreignKey:UserID;references:ID" json:"author,omitempty"`
 	ContentAssets       []*ContentAsset          `gorm:"foreignKey:ContentID;references:ID" json:"content_assets,omitempty"`
 	Comments            []*Comment               `gorm:"foreignKey:ContentID;references:ID" json:"comments,omitempty"`
+	Author              *User                    `gorm:"foreignKey:UserID;references:ID" json:"author,omitempty"`
 }
 
 // Quick operations without importing query package