feat(db): complete deck generation script for top english nouns

- add deck_terms to schema imports
- add addTermsToDeck — diffs source term IDs against existing deck_terms,
  inserts only new ones, returns count of inserted terms
- add updateValidatedLanguages — recalculates and persists validated_languages
  on every run so coverage stays accurate as translation data grows
- wire both functions into main with isNewDeck guard to avoid redundant
  validated_languages update on deck creation
- add final summary report
- fix possible undefined on result[0] in createDeck
- tick off remaining roadmap items

documentation/roadmap.md

@@ -29,10 +29,9 @@ Done when: `GET /api/decks/1/terms?limit=10` returns 10 terms from a specific de
 [x] Write and run migration (includes CHECK constraints for `pos`, `gloss_type`)
 [x] Write `packages/db/src/seed.ts` (imports ALL terms + translations, NO decks)
 [x] Download CEFR A1/A2 noun lists (from GitHub repos)
-[ ] Write `scripts/build_decks.ts` (reads external CEFR lists, matches to DB, creates decks)
-[ ] check notes.md
-[ ] Run `pnpm db:seed` → populates terms
-[ ] Run `pnpm db:build-decks` → creates curated decks
+[x] Write `scripts/build_decks.ts` (reads external CEFR lists, matches to DB, creates decks)
+[x] Run `pnpm db:seed` → populates terms
+[x] Run `pnpm db:build-deck` → creates curated decks
 [ ] Define Zod response schemas in `packages/shared`
 [ ] Implement `DeckRepository.getTerms(deckId, limit, offset)`
 [ ] Implement `QuizService.attachDistractors(terms)` — same POS, server-side, no duplicates