Wire plan_ready, list_ready, new_suggestions and Send to Google Chat

Connect the features to the notification outbox so real events notify,
each stored by the new notify.EmitTx in the transaction of the change it
is about (Wake after commit):

- plan_ready:{weekStart} (/plan) when a draft job stores the AI's draft;
  a redraft shares the key and a manual swap never emits. The title reads
  "Next week's plan is ready" for the coming week.
- list_ready:{weekStart} (/plan/shopping) when a week's Supply run is
  first created, by generate or after Push to Calendar.
- new_suggestions:{batchId} (/discover) when a scheduled or manual batch
  ends done with cards; replenish batches never notify.
- plan.Service.EmitDayOfReminder(date) emits day_of_reminder:{date} for
  the Feature 20 scheduler.

Add POST /api/v1/shopping/{weekStart}/send-chat: shopping.SendToChat posts
the dinners with needed items and a link through chat.PostSupplyRun,
records sent_to_chat_at, and is idempotent per week unless
{"resend": true}. The Supply run's Send to Google Chat button calls it
("Send again" once sent) and shows failures in an ErrorBanner; the unused
Unavailable placeholder is removed.

Task: f0cd9d50-9c11-41be-a945-7bae9f5f28a4

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

migrations/queries/shopping.sql

@@ -89,6 +89,13 @@ UPDATE shopping_lists
 SET title = ?, updated_at = ?
 WHERE id = ? AND title IS NULL AND status = 'current' AND frozen_at IS NULL;
 
+-- name: MarkShoppingListSentToChat :execrows
+-- Records list id sent to Google Chat at sent_to_chat_at, unless it is
+-- frozen into the Supply archive.
+UPDATE shopping_lists
+SET sent_to_chat_at = ?, updated_at = ?
+WHERE id = ? 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.