DuckDB COPY FROM DATABASE memory TO ... can't be parsed

For example:
```sql
COPY FROM DATABASE memory TO my_database;
```

gives the error:
```rs
ParserError("Expected: FROM or TO, found: DATABASE at Line: 1, Column: 11")
```

Documentation: https://duckdb.org/docs/stable/guides/snippets/copy_in-memory_database_to_file.html

Start by reproducing the documented `COPY FROM DATABASE memory TO my_database` statement and trace how the SQL parser handles COPY syntax. Check the existing parser tests for COPY statements, then add coverage for this form; done means the statement parses successfully without the reported error.

Written by the indexing model from the issue text.