feat(client): 三端布局架构 + macOS 桌面端 + app 图标

三端布局(mobile/tablet/desktop):
- core/responsive/form_factor.dart 形态判定 + shell/ 分发器(home_shell→desktop/mobile)
- desktop_shell 对照 ui_kits/desktop/dapp.jsx: 侧栏204·6项 + 套餐卡 + 顶栏(标题/状态/主题切换) + 连接页居中单列
- 新增组件 nav_sidebar / plan_badge_card / content_top_bar / bottom_tab_bar
- 新增一级页 contact_page / settings_page; navigation_provider(NavView)
- 删除旧 widgets/home_shell.dart(逻辑迁入 shell/)

macOS 桌面端:
- 窗口默认 920×600 + 最小 720×560(MainFlutterWindow.swift)
- app 图标替换为穿山甲(AppIcon.appiconset 全套, 由 app-icon.svg 渲染)

其余(本会话):
- Phase2 接线: auth_api/token_store/auth_provider/vpn_bridge_provider + 真实 connection/nodes
- lucide_icons 兼容补丁(packages/lucide_icons_patched) 修复 IconData final 报错
- 测试修复: connect_passthrough(UTF-8) / harness / golden @Skip
- l10n 新增 settingsTitle

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

client/lib/widgets/plan_badge_card.dart

@@ -0,0 +1,64 @@
+// plan_badge_card.dart — 侧栏底部套餐卡（对照 dapp.jsx 侧栏底部）
+//
+// surface 底 + border + radius-md；左 30×30 crown 渐变(clay500→700)，
+// 右两行：套餐名 + 额度/有效期。免费/PRO 两态。
+import 'package:flutter/material.dart';
+import 'package:flutter_riverpod/flutter_riverpod.dart';
+
+import '../pangolin_theme.dart';
+import '../state/app_providers.dart';
+import 'pangolin_icons.dart';
+
+class PlanBadgeCard extends ConsumerWidget {
+  const PlanBadgeCard({super.key});
+
+  @override
+  Widget build(BuildContext context, WidgetRef ref) {
+    final c = context.pangolin;
+    final t = ref.watch(appTextProvider);
+    final isFree = ref.watch(isFreePlanProvider);
+
+    return Container(
+      padding: const EdgeInsets.symmetric(horizontal: 11, vertical: 9),
+      decoration: BoxDecoration(
+        color: c.surface,
+        border: Border.all(color: c.border),
+        borderRadius: BorderRadius.circular(PangolinRadius.md),
+      ),
+      child: Row(children: [
+        Container(
+          width: 30,
+          height: 30,
+          decoration: const BoxDecoration(
+            shape: BoxShape.circle,
+            gradient: LinearGradient(
+              begin: Alignment.topLeft,
+              end: Alignment.bottomRight,
+              colors: [PangolinColors.clay500, PangolinColors.clay700],
+            ),
+          ),
+          child: const Icon(PangolinIcons.crown, size: 15, color: PangolinColors.white),
+        ),
+        const SizedBox(width: 10),
+        Expanded(
+          child: Column(
+            crossAxisAlignment: CrossAxisAlignment.start,
+            mainAxisSize: MainAxisSize.min,
+            children: [
+              Text(
+                isFree ? t.freePlanName : t.proMember,
+                overflow: TextOverflow.ellipsis,
+                style: PangolinText.caption.copyWith(color: c.fg1, fontWeight: FontWeight.w600, fontSize: 12),
+              ),
+              Text(
+                isFree ? t.quotaFree : t.expires,
+                overflow: TextOverflow.ellipsis,
+                style: PangolinText.caption.copyWith(color: c.fg3, fontSize: 10.5),
+              ),
+            ],
+          ),
+        ),
+      ]),
+    );
+  }
+}