- Add /api/admin/embeddings/dimension (GET column dim, POST test model dim)
- Add /api/admin/embeddings/migrate (alter column, clear, re-index)
- Admin form warns on dimension mismatch after save, offers migrate button
- Remove hardcoded 1536 from validate endpoint and embedding service
- Add validateDimension() utility to EmbeddingService
- Fix health route: import prisma correctly, use router instead of missing registry
- i18n keys for dimension warning (EN/FR)
