feat: 健康仪表盘配色调整 + 登录页品牌升级 + iOS 配置 + 隐私文案修订 + 文档清理

## UI 配色
- 健康仪表盘: 背景从蓝紫粉三色渐变改为 #4FACFE 纯色蓝, 白字清晰不抢眼
- app_colors / app_design_tokens / app_theme: 配色体系微调
- 多个 widget 和页面跟随配色更新(health_drawer/admin_drawer/doctor_drawer/enterprise_widgets 等)

## 登录页品牌升级
- 新增品牌素材: drawer_background_v2 / login_background_v2 / health_login_character_transparent
- login_page 重构, 接入新品牌视觉
- app.dart 启动流程调整

## iOS / Android 配置
- Info.plist: 权限描述调整
- AppIcon / LaunchImage: 资源更新
- AndroidManifest: 权限微调

## 隐私文案修订
- privacy.html: 蓝牙设备描述调整为"标准蓝牙血压服务", 移除未上线设备类型表述
- terms.html: 移除"在线医生咨询"相关条款, 服务范围收窄

## 通知中心
- notification_center_page: 重构通知项布局

## 其他
- 删除已完成的计划/spec 文档(ui-system-first-pass / apple-sign-in / secondary-page-color-refresh / notification-preferences-design / ui-design-system)
- 新增 native_navigation_test
- 新增 HANDOFF 交接文档
- home_message_order_test 更新
- .gitignore 调整

health_app/test/home_message_order_test.dart

@@ -108,14 +108,15 @@ void main() {
     expect(source, contains('const SizedBox(height: 22)'));
   });
 
-  test('home drawer follows the native drag gesture', () {
+  test('home drawer gesture is limited to the conversation stream', () {
     final source = File('lib/pages/home/home_page.dart').readAsStringSync();
 
-    expect(source, contains('drawerEnableOpenDragGesture: true'));
-    expect(source, contains('drawerDragStartBehavior: DragStartBehavior.down'));
-    expect(source, contains('drawerEdgeDragWidth:'));
+    expect(source, contains('drawerEnableOpenDragGesture: false'));
+    expect(
+      source,
+      contains('onHorizontalDragUpdate: _updateConversationDrawerDrag'),
+    );
     expect(source, isNot(contains('_drawerDragStartX')));
-    expect(source, isNot(contains('onHorizontalDragUpdate:')));
   });
 
   test('agent capsules use slightly larger icons and labels', () {
@@ -127,12 +128,11 @@ void main() {
 
     expect(source, contains('width: 18'));
     expect(source, contains('height: 18'));
-    expect(source, contains('Icon(visual.icon, size: 13'));
+    expect(source, contains('visual.icon,'));
+    expect(source, contains('size: 13'));
     expect(source, contains('fontSize: 15'));
-    expect(
-      source,
-      contains('selected ? AppColors.actionOutlineGradient : null'),
-    );
+    expect(source, contains('gradient: selected'));
+    expect(source, contains('? AppColors.actionOutlineGradient'));
     expect(source, contains('selected ? null : Colors.transparent'));
     expect(source, contains('color: Colors.white'));
     expect(cards, isNot(contains('LucideIcons.footprints')));