perf: Set tables UNLOGGED before converter COPY in direct-PG mode

[jakebromberg]

Problem

The UNLOGGED table optimization (PR #29) was only applied in `_run_database_build_post_import`, which runs after the Rust converter has already finished writing millions of rows via COPY to LOGGED tables. The heaviest I/O phase (bulk COPY) was still writing WAL.

Solution

Move `set_tables_unlogged` into `_run_xml_pipeline` before the converter call, so the converter's COPY operations target UNLOGGED tables. Remove the redundant call from `_run_database_build_post_import`.

Combined with WXYC/discogs-xml-converter's batch size increase (10K -> 100K), this should significantly reduce the direct-PG pipeline runtime.