Add GET /api/v1/home for the Home dashboard

home.Service aggregates the Home screen from the services that own each
value, at "now" in the household's zone: the date label, tonight's dinner
from the current week's plan (null with no plan), the pending Side quest
count from the deck, the Supply run status of the upcoming week or else
the current one, and recentUpdates.unread.

unread is whether a notification was stored in notification_outbox after
household_settings.updates_seen_at (or at all while it is null), read
through the new notify.StoredSince over the HasNotificationSince query.
Nothing writes updates_seen_at yet; the updates task adds that.

Tests under America/Chicago show tonight's dinner flips at local
midnight, not UTC midnight, and cover no plan, no suggestions, the
Supply run choice and unread.

Maestro task 9ccfc3a6-cc7b-493a-aa4b-2b455d26f4df.

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

docs/ARCHITECTURE.md

@@ -1089,6 +1089,34 @@ Runs are recorded in `schedule_runs` and executed through `jobs`.
   for any other `by`. A frozen list is read through `GET
   /api/v1/shopping/{weekStart}` with `status` `archived`.
 
+## Home API (Feature 21)
+
+- `GET /api/v1/home` (`home.Service`) aggregates the Home screen from the
+  services that own each value, at "now" in the household's zone (never
+  UTC), and answers:
+
+  ```json
+  {
+    "dateLabel": "Friday, Oct 2",
+    "tonight": {"id": "…", "name": "…", "photo": "/media/…", "origin": "regular", "minutes_total": 40},
+    "sideQuestCount": 10,
+    "shoppingList": {"weekStart": "2026-10-05", "label": "Week 41 · Oct 5 – 11", "ready": true, "sentToChatAt": null},
+    "recentUpdates": {"unread": true}
+  }
+  ```
+
+  `tonight` is today's day of the current week's plan (`plan.Get`), null
+  when the week has no plan; it changes at the household's local
+  midnight. `photo` and `minutes_total` are null when unknown.
+  `sideQuestCount` is the pending cards of the deck (`suggest.Deck`).
+  `shoppingList` is the upcoming week's Supply run when it has one, else
+  the current week's (`shopping.Get`); with neither, it is the current
+  week with `ready` false. `recentUpdates.unread` is true when a
+  notification was stored in `notification_outbox` after
+  `household_settings.updates_seen_at`, or at all while that is null
+  (`notify.StoredSince`); an event whose channels are all switched off is
+  never stored and never counts. Nothing writes `updates_seen_at` yet.
+
 ## Frontend
 
 - React 19, TypeScript, Vite, React Router 7, TanStack Query 5,