feat(apps): establish shared mobile design system

apps/heqi_design_system/test/design_system_test.dart

@@ -0,0 +1,39 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_test/flutter_test.dart';
+import 'package:heqi_design_system/heqi_design_system.dart';
+
+void main() {
+  test('two brands share safety semantics but use distinct primary colors', () {
+    final consumer = HeqiTheme.light(HeqiBrand.consumer).colorScheme;
+    final service = HeqiTheme.light(HeqiBrand.service).colorScheme;
+
+    expect(consumer.primary, HeqiColors.consumerPrimary);
+    expect(service.primary, HeqiColors.servicePrimary);
+    expect(consumer.error, HeqiColors.danger);
+    expect(service.error, HeqiColors.danger);
+  });
+
+  testWidgets('status pill exposes a semantic status label', (tester) async {
+    final semantics = tester.ensureSemantics();
+    await tester.pumpWidget(
+      MaterialApp(
+        theme: HeqiTheme.light(HeqiBrand.consumer),
+        home: const Scaffold(
+          body: HeqiStatusPill(label: '已通过', tone: HeqiStatusTone.success),
+        ),
+      ),
+    );
+
+    expect(
+      find.byWidgetPredicate(
+        (widget) => widget is Semantics && widget.properties.label == '状态：已通过',
+      ),
+      findsOneWidget,
+    );
+    semantics.dispose();
+  });
+
+  test('touch target follows Material mobile minimum', () {
+    expect(HeqiSize.minTouchTarget, greaterThanOrEqualTo(48));
+  });
+}