feat(nav): 底部导航图标与文字放大

test/theme/app_dimens_test.dart

@@ -16,11 +16,12 @@ void main() {
     expect(AppDimens.listTitle, 15);
     expect(AppDimens.sectionTitle, 16);
     expect(AppDimens.pageTitle, 20);
-    expect(AppDimens.navLabel, 10);
+    expect(AppDimens.navLabel, 12);
+    expect(AppDimens.navIcon, 24);
     expect(AppDimens.buttonHeight, 48);
     expect(AppDimens.primaryButtonHeight, 52);
     expect(AppDimens.tapTarget, 44);
-    expect(AppDimens.navHeight, 64);
+    expect(AppDimens.navHeight, 68);
     expect(AppDimens.progressHeight, 3);
   });
 }