fix: return errors from deleteSnapshotFromLocalDB instead of swallowing them

Previously, deleteSnapshotFromLocalDB logged errors but always returned nil,
causing callers to believe deletion succeeded even when it failed. This could
lead to data inconsistency where remote metadata is deleted while local
records persist.

Now returns the first error encountered, allowing callers to handle failures
appropriately.

internal/vaultik/snapshot.go

@@ -1003,16 +1003,16 @@ func (v *Vaultik) deleteSnapshotFromLocalDB(snapshotID string) error {
 
 	// Delete related records first to avoid foreign key constraints
 	if err := v.Repositories.Snapshots.DeleteSnapshotFiles(v.ctx, snapshotID); err != nil {
-		log.Error("Failed to delete snapshot files", "snapshot_id", snapshotID, "error", err)
+		return fmt.Errorf("deleting snapshot files for %s: %w", snapshotID, err)
 	}
 	if err := v.Repositories.Snapshots.DeleteSnapshotBlobs(v.ctx, snapshotID); err != nil {
-		log.Error("Failed to delete snapshot blobs", "snapshot_id", snapshotID, "error", err)
+		return fmt.Errorf("deleting snapshot blobs for %s: %w", snapshotID, err)
 	}
 	if err := v.Repositories.Snapshots.DeleteSnapshotUploads(v.ctx, snapshotID); err != nil {
-		log.Error("Failed to delete snapshot uploads", "snapshot_id", snapshotID, "error", err)
+		return fmt.Errorf("deleting snapshot uploads for %s: %w", snapshotID, err)
 	}
 	if err := v.Repositories.Snapshots.Delete(v.ctx, snapshotID); err != nil {
-		log.Error("Failed to delete snapshot record", "snapshot_id", snapshotID, "error", err)
+		return fmt.Errorf("deleting snapshot record %s: %w", snapshotID, err)
 	}
 
 	return nil