fix: sync counters on every CreateIssue to prevent race conditions

Move counter sync from import to CreateIssue to handle parallel issue creation.
This ensures the counter is always up-to-date before generating new IDs,
preventing collisions when multiple processes create issues concurrently.

Remove unused SyncCounterForPrefix method and its test.

internal/storage/sqlite/sqlite.go

@@ -107,22 +107,6 @@ func (s *SQLiteStorage) getNextIDForPrefix(ctx context.Context, prefix string) (
 	return nextID, nil
 }
 
-// SyncCounterForPrefix synchronizes the counter to be at least the given value
-// This is used after importing issues with explicit IDs to prevent ID collisions
-// with subsequently auto-generated IDs
-func (s *SQLiteStorage) SyncCounterForPrefix(ctx context.Context, prefix string, minValue int) error {
-	_, err := s.db.ExecContext(ctx, `
-		INSERT INTO issue_counters (prefix, last_id)
-		VALUES (?, ?)
-		ON CONFLICT(prefix) DO UPDATE SET
-			last_id = MAX(last_id, ?)
-	`, prefix, minValue, minValue)
-	if err != nil {
-		return fmt.Errorf("failed to sync counter for prefix %s: %w", prefix, err)
-	}
-	return nil
-}
-
 // SyncAllCounters synchronizes all ID counters based on existing issues in the database
 // This scans all issues and updates counters to prevent ID collisions with auto-generated IDs
 func (s *SQLiteStorage) SyncAllCounters(ctx context.Context) error {