Initial commit: suixinkan_ios UIKit rewrite project.

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

suixinkan_ios/Features/Main/ViewControllers/PlaceholderViewController.swift

@@ -0,0 +1,41 @@
+//
+//  PlaceholderViewController.swift
+//  suixinkan
+//
+
+import SnapKit
+import UIKit
+
+/// 未知或未实现路由的占位页。
+final class PlaceholderViewController: UIViewController {
+
+    private let pageTitle: String
+
+    init(title: String) {
+        pageTitle = title
+        super.init(nibName: nil, bundle: nil)
+    }
+
+    @available(*, unavailable)
+    required init?(coder: NSCoder) {
+        fatalError("init(coder:) has not been implemented")
+    }
+
+    override func viewDidLoad() {
+        super.viewDidLoad()
+        view.backgroundColor = UIColor(hex: 0xF5F7FA)
+        title = pageTitle
+
+        let label = UILabel()
+        label.text = pageTitle
+        label.font = .systemFont(ofSize: AppMetrics.FontSize.title2, weight: .semibold)
+        label.textColor = AppDesign.textPrimary
+        label.textAlignment = .center
+        label.numberOfLines = 0
+        view.addSubview(label)
+        label.snp.makeConstraints { make in
+            make.center.equalToSuperview()
+            make.leading.trailing.equalToSuperview().inset(AppMetrics.Spacing.large)
+        }
+    }
+}