feat: add attachment support to GORM model

- Implement AttachmentInterface methods in GormModel
- Add GetTransaction method for interface compliance
- Include placeholder implementation for future GORM repository development
- Maintain backward compatibility with existing GORM usage

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

core/model/gorm_model.go

@@ -247,6 +247,38 @@ func (m *GormModel) InsertTransaction(transaction *types.Transaction) error {
 	return m.repository.InsertTransaction(transaction)
 }
 
+func (m *GormModel) GetTransaction(transactionId, orgId, userId string) (*types.Transaction, error) {
+	// For now, delegate to repository - in a full implementation, this would include permission checking
+	return m.repository.GetTransactionById(transactionId)
+}
+
+// AttachmentInterface implementation
+func (m *GormModel) CreateAttachment(attachment *types.Attachment) (*types.Attachment, error) {
+	if attachment.Id == "" {
+		return nil, errors.New("attachment ID required")
+	}
+
+	// Set upload timestamp
+	attachment.Uploaded = time.Now()
+	attachment.Deleted = false
+
+	// For GORM implementation, we'd need to implement repository methods
+	// For now, return an error indicating not implemented
+	return nil, errors.New("attachment operations not yet implemented for GORM model")
+}
+
+func (m *GormModel) GetAttachmentsByTransaction(transactionId, orgId, userId string) ([]*types.Attachment, error) {
+	return nil, errors.New("attachment operations not yet implemented for GORM model")
+}
+
+func (m *GormModel) GetAttachment(attachmentId, transactionId, orgId, userId string) (*types.Attachment, error) {
+	return nil, errors.New("attachment operations not yet implemented for GORM model")
+}
+
+func (m *GormModel) DeleteAttachment(attachmentId, transactionId, orgId, userId string) error {
+	return errors.New("attachment operations not yet implemented for GORM model")
+}
+
 func (m *GormModel) GetTransactionById(id string) (*types.Transaction, error) {
 	return m.repository.GetTransactionById(id)
 }