Add notification preferences API and screen (1n)

GET/PUT /api/v1/settings/notifications read and replace the event x
{push, chat} matrix for the five events and the reminder time. The PUT
validates every event exactly once and an HH:MM time, refuses unknown
events and fields, and writes the preferences and the household
settings' reminder_time (the one copy) in one transaction, publishing
the new settings to the scheduler as a household settings change does.

/settings/notifications renders mock 1n: the matrix with Toggle
switches, including the next-day "Keep it in rotation?" Rotation check
(D-021); the reminder time edited in a sheet; the push permission row
using pushStatus/subscribePush/unsubscribePush; the iOS InstallHint;
the Google Chat webhook card with the masked URL, "Connected · {space}"
and Send test showing success or the HTTP status; and the preview
bubble. The desktop 2e Notifications & AI tab shows the matrix and
webhook cards in its left column. The settings home row now reads Web
Push on this device and the Google Chat space, and the Household form
takes a reminder time saved elsewhere without undoing it.

Maestro task 308a460d-b22c-4179-acba-d5ea0968ccd5.

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

internal/household/settings.go

@@ -187,56 +187,9 @@ func (s *SettingsService) Update(ctx context.Context, patch SettingsPatch, updat
 
 	var row db.HouseholdSetting
 	err := s.st.WithTx(ctx, func(tx *sql.Tx) error {
-		q := db.New(tx)
-		cur, err := q.GetHouseholdSettings(ctx)
-		if err != nil {
-			return fmt.Errorf("household: read settings: %w", err)
-		}
-		p := db.UpsertHouseholdSettingsParams{
-			Timezone:              cur.Timezone,
-			DinnerTime:            cur.DinnerTime,
-			ReminderTime:          cur.ReminderTime,
-			ReviewTime:            cur.ReviewTime,
-			PlanDraftDow:          cur.PlanDraftDow,
-			PlanDraftTime:         cur.PlanDraftTime,
-			SuggestionsDow:        cur.SuggestionsDow,
-			SuggestionsTime:       cur.SuggestionsTime,
-			ChatAutosendDow:       cur.ChatAutosendDow,
-			ChatAutosendTime:      cur.ChatAutosendTime,
-			OnboardingCompletedAt: cur.OnboardingCompletedAt,
-			UpdatesSeenAt:         cur.UpdatesSeenAt,
-			UpdatedBy:             sql.NullString{String: updatedBy, Valid: true},
-			CreatedAt:             cur.CreatedAt,
-			UpdatedAt:             store.Now().String(),
-		}
-		setString(&p.Timezone, patch.Timezone)
-		setString(&p.DinnerTime, patch.DinnerTime)
-		setString(&p.ReminderTime, patch.ReminderTime)
-		setString(&p.ReviewTime, patch.ReviewTime)
-		setDow(&p.PlanDraftDow, patch.PlanDraftDow)
-		setString(&p.PlanDraftTime, patch.PlanDraftTime)
-		setDow(&p.SuggestionsDow, patch.SuggestionsDow)
-		setString(&p.SuggestionsTime, patch.SuggestionsTime)
-		setDow(&p.ChatAutosendDow, patch.ChatAutosendDow)
-		setString(&p.ChatAutosendTime, patch.ChatAutosendTime)
-		if patch.OnboardingCompleted != nil && !p.OnboardingCompletedAt.Valid {
-			n, err := q.CountRegularDinners(ctx)
-			if err != nil {
-				return fmt.Errorf("household: count Regulars: %w", err)
-			}
-			if n < MinRegulars {
-				return &ValidationError{Problems: []Problem{{
-					Field:  "onboarding_completed",
-					Reason: fmt.Sprintf("add at least %d Regulars first (have %d)", MinRegulars, n),
-				}}}
-			}
-			p.OnboardingCompletedAt = sql.NullString{String: p.UpdatedAt, Valid: true}
-		}
-		row, err = q.UpsertHouseholdSettings(ctx, p)
-		if err != nil {
-			return fmt.Errorf("household: update settings: %w", err)
-		}
-		return nil
+		var err error
+		row, err = applyPatch(ctx, db.New(tx), patch, updatedBy)
+		return err
 	})
 	if err != nil {
 		return Settings{}, err
@@ -247,8 +200,62 @@ func (s *SettingsService) Update(ctx context.Context, patch SettingsPatch, updat
 	return settings, 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) {
+	cur, err := q.GetHouseholdSettings(ctx)
+	if err != nil {
+		return db.HouseholdSetting{}, fmt.Errorf("household: read settings: %w", err)
+	}
+	p := db.UpsertHouseholdSettingsParams{
+		Timezone:              cur.Timezone,
+		DinnerTime:            cur.DinnerTime,
+		ReminderTime:          cur.ReminderTime,
+		ReviewTime:            cur.ReviewTime,
+		PlanDraftDow:          cur.PlanDraftDow,
+		PlanDraftTime:         cur.PlanDraftTime,
+		SuggestionsDow:        cur.SuggestionsDow,
+		SuggestionsTime:       cur.SuggestionsTime,
+		ChatAutosendDow:       cur.ChatAutosendDow,
+		ChatAutosendTime:      cur.ChatAutosendTime,
+		OnboardingCompletedAt: cur.OnboardingCompletedAt,
+		UpdatesSeenAt:         cur.UpdatesSeenAt,
+		UpdatedBy:             sql.NullString{String: updatedBy, Valid: true},
+		CreatedAt:             cur.CreatedAt,
+		UpdatedAt:             store.Now().String(),
+	}
+	setString(&p.Timezone, patch.Timezone)
+	setString(&p.DinnerTime, patch.DinnerTime)
+	setString(&p.ReminderTime, patch.ReminderTime)
+	setString(&p.ReviewTime, patch.ReviewTime)
+	setDow(&p.PlanDraftDow, patch.PlanDraftDow)
+	setString(&p.PlanDraftTime, patch.PlanDraftTime)
+	setDow(&p.SuggestionsDow, patch.SuggestionsDow)
+	setString(&p.SuggestionsTime, patch.SuggestionsTime)
+	setDow(&p.ChatAutosendDow, patch.ChatAutosendDow)
+	setString(&p.ChatAutosendTime, patch.ChatAutosendTime)
+	if patch.OnboardingCompleted != nil && !p.OnboardingCompletedAt.Valid {
+		n, err := q.CountRegularDinners(ctx)
+		if err != nil {
+			return db.HouseholdSetting{}, fmt.Errorf("household: count Regulars: %w", err)
+		}
+		if n < MinRegulars {
+			return db.HouseholdSetting{}, &ValidationError{Problems: []Problem{{
+				Field:  "onboarding_completed",
+				Reason: fmt.Sprintf("add at least %d Regulars first (have %d)", MinRegulars, n),
+			}}}
+		}
+		p.OnboardingCompletedAt = sql.NullString{String: p.UpdatedAt, Valid: true}
+	}
+	row, err := q.UpsertHouseholdSettings(ctx, p)
+	if err != nil {
+		return db.HouseholdSetting{}, fmt.Errorf("household: update settings: %w", err)
+	}
+	return row, nil
+}
+
 // Subscribe registers fn to receive the new settings after every successful
-// Update. fn runs synchronously on the updating goroutine, so it must return
+// Update and UpdateNotifications. fn runs synchronously on the updating goroutine, so it must return
 // promptly and must not call Update. The returned function unsubscribes fn.
 func (s *SettingsService) Subscribe(fn func(Settings)) (unsubscribe func()) {
 	s.subsMu.Lock()