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/suggest/suggest.go

@@ -346,6 +346,17 @@ func (s *Service) Deck(ctx context.Context) (Deck, error) {
 	return deck, nil
 }
 
+// PendingCount is how many Side quests are pending on the deck. Unlike
+// Deck it only reads: it does not fail orphaned batches, so a reader such
+// as Home never writes.
+func (s *Service) PendingCount(ctx context.Context) (int, error) {
+	rows, err := db.New(s.st.Reader).ListDeck(ctx)
+	if err != nil {
+		return 0, fmt.Errorf("suggest: list deck: %w", err)
+	}
+	return len(rows), nil
+}
+
 // Decision is a suggestion once decided, with the id of the replenish
 // batch's job when the decision called for one: the batch it started, or
 // the one already pending or running that it joined.