Add the Recent updates sheet behind the Home bell (Feature 21)

GET /api/v1/updates lists the last 10 distinct notification events from
the outbox, newest first and one per event key whatever its channels.
POST /api/v1/updates/seen {"through": created_at} moves
household_settings.updates_seen_at forward, so /api/v1/home's
recentUpdates.unread is true only for an event stored since. The Home
bell opens a Sheet listing the updates with relative times; a row opens
its URL, and opening the sheet marks the updates seen, clearing the
grape dot optimistically and putting it back if the mark fails.

Maestro task 96e2dc3f-1f8a-4114-bcb5-e0f93c349165.

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

internal/household/settings.go

@@ -8,6 +8,7 @@ import (
 	"regexp"
 	"strings"
 	"sync"
+	"time"
 
 	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/db"
 	"code.cubecraftlabs.com/Maniacs_Mansion/Meal-Quest/internal/store"
@@ -200,6 +201,21 @@ func (s *SettingsService) Update(ctx context.Context, patch SettingsPatch, updat
 	return settings, nil
 }
 
+// MarkUpdatesSeen records that the household has seen its Recent updates
+// through seenAt: updates_seen_at moves forward to seenAt, and is left as it
+// is when it is already at or after it. It is not a settings edit, so
+// updated_by and updated_at are kept and subscribers are not told.
+func (s *SettingsService) MarkUpdatesSeen(ctx context.Context, seenAt time.Time) error {
+	if seenAt.IsZero() {
+		return errors.New("household: mark updates seen: zero time")
+	}
+	_, err := db.New(s.st.Writer).MarkUpdatesSeen(ctx, store.Timestamp{Time: seenAt.UTC().Truncate(time.Millisecond)}.String())
+	if err != nil {
+		return fmt.Errorf("household: mark updates seen: %w", err)
+	}
+	return nil
+}
+
 // applyPatch applies a validated patch to the household settings row in q's
 // transaction, recording updatedBy, and returns the new row.
 func applyPatch(ctx context.Context, q *db.Queries, patch SettingsPatch, updatedBy string) (db.HouseholdSetting, error) {