fix(migration): simplify aisle migration + add persistent backup script

- Drop the empty batch_alter_table block and the meaningless
  set_config call from migration 0015. Temp tables still persist
  for the migration's session (Alembic's transactional_ddl).
- New backend/scripts/persist_aisle_backup.sql creates
  public.ingredient_aisle_backup_0015 and
  public.grocery_item_aisle_backup_0015 permanent tables for
  operators who want a recoverable record beyond the migration.
- Update Review/sprint2-verification.md, Review/ui-nielsen-audit.md
  and fix-ui-audit.md with the correct container-based deploy
  steps: docker compose exec db psql -U mealplanner -d mealplanner
  -f /dev/stdin < ...sql. Host psql is not available on the
  deployment host; the db runs inside the container.

Review/ui-nielsen-audit.md

@@ -30,13 +30,23 @@ The app looks polished on the surface (Tailwind palette, clean cards, working to
 > - **B11** Recipes filters: refactored to `pending`/`applied` state with explicit Apply / Reset buttons. `Filters` button shows active-count chip when filters are set. Wrapped in `role="region" aria-label="Filters"`.
 > - **S3.3** Shopping list stat cards: now `grid-cols-3` on all viewports with compact mobile sizing.
 >
-> Deployment command:
+> Deployment commands (run on the deployment host — DB is in a container, no host psql needed):
 > ```bash
-> # On the deployment host:
+> cd ~/MealPlanner
 > git pull
-> # Apply the backend migration (one-off):
+>
+> # Optional: persistent backup of aisle values BEFORE the migration
+> docker compose exec -T db psql -U mealplanner -d mealplanner \
+>   -f /dev/stdin < backend/scripts/persist_aisle_backup.sql
+>
+> # Dry-run preview (no writes)
+> docker compose exec -T db psql -U mealplanner -d mealplanner \
+>   -f /dev/stdin < backend/scripts/dry_run_aisle_migration.sql
+>
+> # Apply the migration
 > docker compose exec backend alembic upgrade head
-> # Rebuild & restart frontend:
+>
+> # Rebuild & restart frontend
 > docker compose -f docker-compose.yml up -d --build frontend
 > ```