Root causes:
- Seed selection sorted by controversy_score across all 28k motions, but
only 282 have individual MP vote records. Top controversial motions only
have party-level votes, so match_mps_for_votes always returned empty.
- global_db singleton was used for match/discriminate instead of the db_path
passed to the tab builder.
Fixes:
- Add MotionDatabase.get_motions_with_individual_votes(k) which queries
motions with comma-formatted mp_name votes, ordered by controversy_score
- Replace broken seed logic in build_mp_quiz_tab with this new method
- Replace global_db usages with a local MotionDatabase(db_path) instance
- Guard against motion IDs present in votes but absent from motions DataFrame
Sven Geboers