Fix SQLite export path handling and WHEEL table constraints

[Jopo-JP]

This PR addresses two issues in the SQLite exporter:

1. Output Path Handling: Fixed a DirectoryNotFoundException when providing a directory as the output argument (e.g., -o ./). The tool now correctly appends the SpecDB name to the path if a directory is provided.
2. WHEEL Table Constraint: Removed the PRIMARY KEY constraint for the WHEEL table. This fixes a crash (UNIQUE constraint failed) occurring with certain SpecDB versions (like GT5) that contain duplicate RowIds in the WHEEL table.