Add WorkflowRun and AlbumEvent repositories with download cancel support

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/claude-agent)

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

internal/database/download_repository.go

@@ -86,6 +86,26 @@ func (r *DownloadRepository) SetFailed(ctx context.Context, id string, errorMsg
 	return nil
 }
 
+func (r *DownloadRepository) SetCancelled(ctx context.Context, id string) error {
+	_, err := r.pool.Exec(ctx,
+		`UPDATE downloads SET state = 'cancelled', updated_at = NOW() WHERE id = $1`, id,
+	)
+	if err != nil {
+		return fmt.Errorf("setting download cancelled: %w", err)
+	}
+	return nil
+}
+
+func (r *DownloadRepository) SetCancelledByQbitHash(ctx context.Context, hash string) error {
+	_, err := r.pool.Exec(ctx,
+		`UPDATE downloads SET state = 'cancelled', updated_at = NOW() WHERE qbit_hash = $1 AND state NOT IN ('completed', 'failed', 'cancelled')`, hash,
+	)
+	if err != nil {
+		return fmt.Errorf("setting download cancelled by hash: %w", err)
+	}
+	return nil
+}
+
 func (r *DownloadRepository) GetByAlbumID(ctx context.Context, albumID string) ([]*Download, error) {
 	rows, err := r.pool.Query(ctx,
 		`SELECT id, torrent_id, album_id, format, quality, state, qbit_hash, save_path, error_message, queued_at, started_at, completed_at, created_at, updated_at