18 glossaries accumulated from multiple imports. This migration:
1. Deletes ALL glossaries with target_language='en' (old stale imports)
2. Deduplicates multilingual glossaries keeping only the newest per name
Result: 8 clean glossaries (one per template), all marked as multilingual.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
