Answer push_off before no_subscriptions and give every iOS browser the Home Screen copy (Feature 19)

SendTest now reads the plan_ready push preference before the stored
subscriptions, so with push off and no device subscribed the test-push
endpoint answers 409 push_off rather than 409 no_subscriptions.

Onboarding step 3's unsupported result now gives the Home Screen guidance
in any iOS browser, not only Safari. isIos in InstallHint.tsx is the one
check for iPhone, iPod and iPad; isIosSafari builds on it and InstallHint
itself stays Safari-only.

Task f89279b8-b92c-4d9f-a6c2-fd87fccda509

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

internal/push/push_test.go

@@ -306,3 +306,20 @@ func TestSendTestWithPushOff(t *testing.T) {
 		t.Fatalf("rows = %+v, want none", rows)
 	}
 }
+
+// Push off is reported before the subscriptions are looked at, so with
+// both push off and no device subscribed the answer is push off.
+func TestSendTestWithPushOffAndNoSubscriptions(t *testing.T) {
+	t.Parallel()
+	svc, st := newTestService(t)
+	if _, err := st.Writer.Exec(`UPDATE notification_prefs SET push = 0 WHERE event = 'plan_ready'`); err != nil {
+		t.Fatal(err)
+	}
+	_, err := svc.SendTest(context.Background())
+	if !errors.Is(err, notify.ErrPushOff) || errors.Is(err, ErrNoSubscriptions) {
+		t.Fatalf("SendTest = %v, want notify.ErrPushOff", err)
+	}
+	if rows := notifytest.Rows(t, st, notify.PlanReady); len(rows) != 0 {
+		t.Fatalf("rows = %+v, want none", rows)
+	}
+}