fix: harden deepseek official remote43 import closure

internal/store/sqlite/db.go

@@ -44,6 +44,11 @@ func Open(ctx context.Context, dsn string) (*DB, error) {
 	if err != nil {
 		return nil, fmt.Errorf("open sqlite database: %w", err)
 	}
+	// SQLite only tolerates a single writer at a time. Pin the pool to one
+	// connection so HTTP flows that chain several writes (for example host
+	// probe refresh + import persistence) do not self-deadlock into SQLITE_BUSY.
+	sqlDB.SetMaxOpenConns(1)
+	sqlDB.SetMaxIdleConns(1)
 
 	if err := sqlDB.PingContext(ctx); err != nil {
 		_ = sqlDB.Close()