Freeze ended weeks into the Supply archive and serve the archive API (Feature 17)

shopping.Freeze(weekStart) archives a week's Supply run once its week has
ended in the household's time zone, setting status archived and frozen_at;
it is idempotent, and a week not yet ended (ErrWeekNotEnded) or with no
list (ErrListNotFound) is an explicit error. A list still untitled is
titled first with archive_title and the same conditional write the
title_supply_run job uses; a failed title is logged and the list is
frozen untitled, keeping its week label.

GET /api/v1/shopping/archive?by=week|month|year returns the Supply runs
up to the household's current week, newest first, grouped by the
Monday's ISO week, month or year, each post with its week label, title or
null, dinner, item and on-hand counts, dinner names and current flag. Any
other by is 400 invalid_request. Frozen lists stay readable through
GET /shopping/{weekStart} and reject item PATCHes with 409 archived.

Maestro task 7ac36526-cb51-4dc7-bbad-6ebbee481942.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

migrations/queries/shopping.sql

@@ -88,3 +88,17 @@ WHERE id = ?;
 UPDATE shopping_lists
 SET title = ?, updated_at = ?
 WHERE id = ? AND title IS NULL AND status = 'current' AND frozen_at IS NULL;
+
+-- name: FreezeShoppingList :execrows
+-- Freezes list id into the Supply archive at frozen_at, unless it is
+-- frozen already.
+UPDATE shopping_lists
+SET status = 'archived', frozen_at = ?, updated_at = ?
+WHERE id = ? AND frozen_at IS NULL;
+
+-- name: ListShoppingListsThrough :many
+-- The Supply runs of the weeks starting on or before week_start, newest
+-- week first.
+SELECT * FROM shopping_lists
+WHERE week_start <= ?
+ORDER BY week_start DESC;