Add login flow, session routing, and MainTab shell aligned with reference UI.

Implement token-based root routing, Android-matched login screen, five-slot MainTabBar with scan action, and placeholder tab pages.

Co-authored-by: Cursor <cursoragent@cursor.com>

suixinkan/UI/Orders/OrdersViewController.swift

@@ -0,0 +1,28 @@
+//
+//  OrdersViewController.swift
+//  suixinkan
+//
+
+import SnapKit
+import UIKit
+
+/// 订单 Tab 根页面。
+final class OrdersViewController: BaseViewController {
+
+    private let titleLabel = UILabel()
+
+    override func setupUI() {
+        title = "订单"
+        titleLabel.text = "订单"
+        titleLabel.font = .systemFont(ofSize: 24, weight: .medium)
+        titleLabel.textAlignment = .center
+        titleLabel.textColor = AppColor.text333
+        view.addSubview(titleLabel)
+    }
+
+    override func setupConstraints() {
+        titleLabel.snp.makeConstraints { make in
+            make.center.equalToSuperview()
+        }
+    }
+}