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.

backend/scripts/persist_aisle_backup.sql

@@ -0,0 +1,24 @@
+-- Persist a permanent backup of aisle values BEFORE running migration 0015.
+-- Run via Docker (no host psql required):
+--
+--   docker compose exec db psql -U mealplanner -d mealplanner \
+--     -f /dev/stdin < backend/scripts/persist_aisle_backup.sql
+--
+-- Creates two permanent backup tables in the public schema. They are NOT
+-- auto-dropped; you can DROP them manually after you confirm the migration
+-- is correct:
+--
+--   DROP TABLE public.ingredient_aisle_backup_0015;
+--   DROP TABLE public.grocery_item_aisle_backup_0015;
+
+CREATE TABLE IF NOT EXISTS public.ingredient_aisle_backup_0015 AS
+  SELECT id, aisle, created_at FROM public.ingredient WHERE aisle IS NOT NULL;
+
+CREATE TABLE IF NOT EXISTS public.grocery_item_aisle_backup_0015 AS
+  SELECT id, aisle FROM public.grocery_item WHERE aisle IS NOT NULL;
+
+SELECT 'ingredient backup'   AS table_name, COUNT(*) AS rows_backed_up
+  FROM public.ingredient_aisle_backup_0015
+UNION ALL
+SELECT 'grocery_item backup' AS table_name, COUNT(*) AS rows_backed_up
+  FROM public.grocery_item_aisle_backup_0015;