fix: SQLITE_BUSY при клонировании конфигурации вариантов

SetMaxOpenConns(1) сериализует запись через единственное соединение,
busy_timeout=5000 добавляет ожидание до 5с при внешних блокировках.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

internal/localdb/localdb.go

@@ -114,6 +114,13 @@ func New(dbPath string) (*LocalDB, error) {
 		return nil, fmt.Errorf("opening sqlite database: %w", err)
 	}
 
+	// SQLite requires a single writer connection to avoid SQLITE_BUSY under concurrent requests.
+	sqlDB, err := db.DB()
+	if err != nil {
+		return nil, fmt.Errorf("get sql.DB from gorm: %w", err)
+	}
+	sqlDB.SetMaxOpenConns(1)
+
 	// Enable WAL mode so background sync writes never block UI reads.
 	if err := db.Exec("PRAGMA journal_mode=WAL").Error; err != nil {
 		slog.Warn("failed to enable WAL mode", "error", err)
@@ -121,6 +128,10 @@ func New(dbPath string) (*LocalDB, error) {
 	if err := db.Exec("PRAGMA synchronous=NORMAL").Error; err != nil {
 		slog.Warn("failed to set synchronous=NORMAL", "error", err)
 	}
+	// Wait up to 5 s before returning SQLITE_BUSY (guards against WAL checkpoints and external locks).
+	if err := db.Exec("PRAGMA busy_timeout = 5000").Error; err != nil {
+		slog.Warn("failed to set busy_timeout", "error", err)
+	}
 
 	if err := ensureLocalProjectsTable(db); err != nil {
 		return nil, fmt.Errorf("ensure local_projects table: %w", err)