feat(store): add blob, file, folder, and upload stores

Add BlobStore (ref counting), FileStore (soft delete + pagination), FolderStore (materialized path), UploadStore (idempotent upsert), and update AutoMigrate.

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

internal/store/file_store.go

@@ -0,0 +1,99 @@
+package store
+
+import (
+	"context"
+	"errors"
+
+	"gcy_hpc_server/internal/model"
+
+	"gorm.io/gorm"
+)
+
+type FileStore struct {
+	db *gorm.DB
+}
+
+func NewFileStore(db *gorm.DB) *FileStore {
+	return &FileStore{db: db}
+}
+
+func (s *FileStore) Create(ctx context.Context, file *model.File) error {
+	return s.db.WithContext(ctx).Create(file).Error
+}
+
+func (s *FileStore) GetByID(ctx context.Context, id int64) (*model.File, error) {
+	var file model.File
+	err := s.db.WithContext(ctx).First(&file, id).Error
+	if errors.Is(err, gorm.ErrRecordNotFound) {
+		return nil, nil
+	}
+	if err != nil {
+		return nil, err
+	}
+	return &file, nil
+}
+
+func (s *FileStore) List(ctx context.Context, folderID *int64, page, pageSize int) ([]model.File, int64, error) {
+	query := s.db.WithContext(ctx).Model(&model.File{})
+	if folderID == nil {
+		query = query.Where("folder_id IS NULL")
+	} else {
+		query = query.Where("folder_id = ?", *folderID)
+	}
+
+	var total int64
+	if err := query.Count(&total).Error; err != nil {
+		return nil, 0, err
+	}
+
+	var files []model.File
+	offset := (page - 1) * pageSize
+	if err := query.Order("id DESC").Limit(pageSize).Offset(offset).Find(&files).Error; err != nil {
+		return nil, 0, err
+	}
+	return files, total, nil
+}
+
+func (s *FileStore) Search(ctx context.Context, queryStr string, page, pageSize int) ([]model.File, int64, error) {
+	query := s.db.WithContext(ctx).Model(&model.File{}).Where("name LIKE ?", "%"+queryStr+"%")
+
+	var total int64
+	if err := query.Count(&total).Error; err != nil {
+		return nil, 0, err
+	}
+
+	var files []model.File
+	offset := (page - 1) * pageSize
+	if err := query.Order("id DESC").Limit(pageSize).Offset(offset).Find(&files).Error; err != nil {
+		return nil, 0, err
+	}
+	return files, total, nil
+}
+
+func (s *FileStore) Delete(ctx context.Context, id int64) error {
+	result := s.db.WithContext(ctx).Delete(&model.File{}, id)
+	if result.Error != nil {
+		return result.Error
+	}
+	return nil
+}
+
+func (s *FileStore) CountByBlobSHA256(ctx context.Context, blobSHA256 string) (int64, error) {
+	var count int64
+	err := s.db.WithContext(ctx).Model(&model.File{}).
+		Where("blob_sha256 = ?", blobSHA256).
+		Count(&count).Error
+	return count, err
+}
+
+func (s *FileStore) GetBlobSHA256ByID(ctx context.Context, id int64) (string, error) {
+	var file model.File
+	err := s.db.WithContext(ctx).Select("blob_sha256").First(&file, id).Error
+	if errors.Is(err, gorm.ErrRecordNotFound) {
+		return "", nil
+	}
+	if err != nil {
+		return "", err
+	}
+	return file.BlobSHA256, nil
+}