Add comprehensive test coverage for core functionalities

This commit introduces test cases for the API, archive, store, and filesystem functionalities, as well as a functional test for a full workflow. It ensures robust testing for snapshot operations, archiving, and blob management, significantly improving reliability.

store/sqlite/sqlite.go

@@ -6,7 +6,6 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
-	"gitea.unprism.ru/KRBL/Agate"
 	"gitea.unprism.ru/KRBL/Agate/store"
 	_ "github.com/mattn/go-sqlite3"
 	"os"
@@ -131,7 +130,7 @@ func (s *sqliteStore) GetSnapshotMetadata(ctx context.Context, snapshotID string
 	if err != nil {
 		if errors.Is(err, sql.ErrNoRows) {
 			// Если запись не найдена, возвращаем кастомную ошибку
-			return nil, agate.ErrNotFound
+			return nil, store.ErrNotFound
 		}
 		return nil, fmt.Errorf("failed to query snapshot %s: %w", snapshotID, err)
 	}