feat(client): 全模块 API 对接 + 修复登陆跳转 + 菜单 UI 优化

API 对接：
- 入库/出库/库存/财务/往来单位/基础数据全部对接后端 REST API
- 新增 repositories、providers、models 层，统一分层架构
- auth 从 flutter_secure_storage 迁移到 shared_preferences

登陆跳转修复：
- 将 _RouterNotifier 提取为独立 Riverpod provider，appRouterProvider
  使用 ref.read 避免依赖链导致 router 重建后跳回 /login
- redirect 函数新增 initialized 守卫，防止 auth 未恢复时误重定向
- 添加调试日志（Router/Auth/ApiClient）定位 401 触发的 logout 链路

退出菜单 UI：
- 去掉 ListTile，改用 Row + 自定义 padding，文字左对齐
- MouseRegion + AnimatedContainer 实现 hover 高亮（普通项蓝底/退出红底）
- 菜单圆角 6px，elevation 8，分割线高度 1px

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

client/lib/models/partner.dart

@@ -0,0 +1,46 @@
+class Partner {
+  final int id;
+  final String? code;
+  final String name;
+  final String type; // supplier | customer
+  final String? contact;
+  final String? phone;
+  final String? address;
+  final String? bankAccount;
+  final String? remark;
+
+  const Partner({
+    required this.id,
+    this.code,
+    required this.name,
+    required this.type,
+    this.contact,
+    this.phone,
+    this.address,
+    this.bankAccount,
+    this.remark,
+  });
+
+  factory Partner.fromJson(Map<String, dynamic> json) => Partner(
+        id: (json['id'] as num).toInt(),
+        code: json['code'] as String?,
+        name: json['name'] as String,
+        type: json['type'] as String,
+        contact: json['contact'] as String?,
+        phone: json['phone'] as String?,
+        address: json['address'] as String?,
+        bankAccount: json['bank_account'] as String?,
+        remark: json['remark'] as String?,
+      );
+
+  Map<String, dynamic> toJson() => {
+        'name': name,
+        'type': type,
+        if (code != null) 'code': code,
+        if (contact != null) 'contact': contact,
+        if (phone != null) 'phone': phone,
+        if (address != null) 'address': address,
+        if (bankAccount != null) 'bank_account': bankAccount,
+        if (remark != null) 'remark': remark,
+      };
+}