Fix Home dashboard integration findings (Feature 21)

- F21-01: plan_ready and list_ready links carry their week
  (/plan?week=, /plan/shopping?week=), and the Plan opens on ?week=
  and keeps it on the week shown, so an older update opens its week.
- F21-02: a failed refresh of the Rotation check shows its ErrorBanner
  beside the cached pending card instead of replacing it.
- F21-03: Home carries the household's timezone and is read again at
  its next local midnight.
- F21-04: Home counts pending Side quests through a read-only query
  (suggest.PendingCount), so reading Home never writes batches.

Task: ac3dddf0-a05f-4e43-a5ad-3105fe6bdd95

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

internal/chat/chat_test.go

@@ -342,8 +342,8 @@ func TestSendThreadsByWeek(t *testing.T) {
 		t.Errorf("plan text = %q", reqs[0].Body["text"])
 	}
 
-	// The cards' "Open" buttons link under the public URL.
-	for i, wantLink := range map[int]string{0: "https://mealquest.example/plan", 1: "https://mealquest.example/plan/shopping"} {
+	// The cards' "Open" buttons link under the public URL to the event's week.
+	for i, wantLink := range map[int]string{0: "https://mealquest.example/plan?week=2026-10-12", 1: "https://mealquest.example/plan/shopping?week=2026-10-12"} {
 		data, _ := json.Marshal(reqs[i].Body["cardsV2"])
 		var cards []cardV2
 		if err := json.Unmarshal(data, &cards); err != nil || len(cards) != 1 {