feat: build 3 parallel site variants, one per dataset

Sites:
  /thptqg2017/      → data/      861,068 students (baotintuc.vn .xls)
  /thptqg2017/old/  → data-old/  847,348 students (original xlsx)
  /thptqg2017/old2/ → data-old2/ 679,764 students (update/ overrides)

Build pipeline:
- scripts/build-lib.js: shared schema, score regex, toAscii, insert
  builder — keeps the 3 DBs drop-in compatible for the same frontend
- scripts/build-database.js: multi-sheet walk for baotintuc .xls (HN/HCM
  overflow past the 65k-per-sheet .xls cap)
- scripts/build-database-old.js: single-sheet xlsx + strict numeric SBD
  guard (rejects the header-row leak present in data-old)
- scripts/build-database-old2.js: multi-sheet + blank-row pre-filter for
  the 54 update files (HCM overflow present, HN not in this subset)
- Each build prints a source-vs-DB audit; verified 0 parse errors and
  exact row-count match across all 3 datasets

Frontend plumbing:
- vite.config.js: VARIANT env selects base path, publicDir, outDir
- package.json: build:db:*, build:db:all, build:old, build:old2,
  build:all
- .github/workflows/deploy.yml: CI builds all 3 DBs + sites
- .gitignore: cover public-old/ and public-old2/ outputs
- eslint.config.js: add Node globals for config/script files

2017/.github/workflows/deploy.yml

@@ -28,17 +28,23 @@ jobs:
       - name: Install dependencies
         run: npm ci
 
-      - name: Build database
-        run: npm run build:db
+      - name: Build all databases
+        run: npm run build:db:all
 
-      - name: Compress database
-        run: gzip -k -9 public/thptqg2017.db
+      - name: Compress databases
+        run: |
+          gzip -kf -9 public/thptqg2017.db
+          gzip -kf -9 public-old/thptqg2017.db
+          gzip -kf -9 public-old2/thptqg2017.db
 
-      - name: Build site
-        run: npm run build
+      - name: Build all site variants
+        run: npm run build:all
 
-      - name: Remove uncompressed db from dist
-        run: rm -f dist/thptqg2017.db
+      - name: Drop uncompressed DB files from dist
+        run: |
+          rm -f dist/thptqg2017.db
+          rm -f dist/old/thptqg2017.db
+          rm -f dist/old2/thptqg2017.db
 
       - uses: actions/upload-pages-artifact@v3
         with: