Add Lottie global loading overlay and fix stuck loading states.

Replace per-VC activity indicators with a ref-counted GlobalLoadingManager, and resolve duplicate show/hide calls on Profile, Statistics, and Home tabs.

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

suixinkan/UI/Loading/GlobalLoadingOverlayView.swift

@@ -0,0 +1,53 @@
+//
+//  GlobalLoadingOverlayView.swift
+//  suixinkan
+//
+
+import SnapKit
+import UIKit
+
+/// 全局 Loading 遮罩，对齐 Android `LoadingScrim` 样式。
+final class GlobalLoadingOverlayView: UIView {
+
+    private let cardView = UIView()
+    private let loadingView = LottieLoadingView()
+
+    override init(frame: CGRect) {
+        super.init(frame: frame)
+        backgroundColor = UIColor.black.withAlphaComponent(0.2)
+        isUserInteractionEnabled = true
+
+        cardView.backgroundColor = .white
+        cardView.layer.cornerRadius = 15
+        cardView.clipsToBounds = true
+
+        addSubview(cardView)
+        cardView.addSubview(loadingView)
+
+        cardView.snp.makeConstraints { make in
+            make.center.equalToSuperview()
+            make.width.height.equalTo(100)
+        }
+        loadingView.snp.makeConstraints { make in
+            make.center.equalToSuperview()
+            make.width.height.equalTo(80)
+        }
+    }
+
+    @available(*, unavailable)
+    required init?(coder: NSCoder) {
+        fatalError("init(coder:) has not been implemented")
+    }
+
+    /// 显示并开始动画。
+    func present() {
+        isHidden = false
+        loadingView.startAnimating()
+    }
+
+    /// 隐藏并停止动画。
+    func dismiss() {
+        loadingView.stopAnimating()
+        isHidden = true
+    }
+}