Add Lottie-based global loading overlay across key flows.

Introduce GlobalLoadingCenter with reference counting, wire it through RootView and major auth/order/profile screens, and add the loading animation asset plus unit tests.

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

suixinkanTests/GlobalLoadingCenterTests.swift

@@ -0,0 +1,113 @@
+//
+//  GlobalLoadingCenterTests.swift
+//  suixinkanTests
+//
+//  Created by Codex on 2026/6/23.
+//
+
+import XCTest
+@testable import suixinkan
+
+@MainActor
+/// 全局 Loading 命令中心测试，验证展示状态不会泄漏给业务页面使用。
+final class GlobalLoadingCenterTests: XCTestCase {
+    /// 测试多次 show/hide 会按引用计数控制最终显隐。
+    func testShowHideUsesReferenceCount() {
+        let center = GlobalLoadingCenter()
+
+        center.show(message: "加载账号")
+        center.show(message: "加载权限")
+
+        XCTAssertEqual(center.snapshotForTests, GlobalLoadingSnapshot(isVisible: true, message: "加载权限", activeCount: 2))
+
+        center.hide()
+        XCTAssertEqual(center.snapshotForTests, GlobalLoadingSnapshot(isVisible: true, message: "加载权限", activeCount: 1))
+
+        center.hide()
+        XCTAssertEqual(center.snapshotForTests, GlobalLoadingSnapshot(isVisible: false, message: "", activeCount: 0))
+    }
+
+    /// 测试 hide 调用次数超过 show 时不会产生负数计数。
+    func testHideNeverDropsReferenceCountBelowZero() {
+        let center = GlobalLoadingCenter()
+
+        center.hide()
+
+        XCTAssertEqual(center.snapshotForTests, GlobalLoadingSnapshot(isVisible: false, message: "", activeCount: 0))
+    }
+
+    /// 测试更新文案只影响当前展示内容，不改变引用计数。
+    func testUpdateMessageOnlyChangesVisibleMessage() {
+        let center = GlobalLoadingCenter()
+
+        center.updateMessage("不会展示")
+        XCTAssertEqual(center.snapshotForTests, GlobalLoadingSnapshot(isVisible: false, message: "", activeCount: 0))
+
+        center.show(message: "加载中")
+        center.updateMessage("即将完成")
+
+        XCTAssertEqual(center.snapshotForTests, GlobalLoadingSnapshot(isVisible: true, message: "即将完成", activeCount: 1))
+    }
+
+    /// 测试 withLoading 成功完成后自动隐藏 Loading。
+    func testWithLoadingHidesAfterSuccess() async throws {
+        let center = GlobalLoadingCenter()
+
+        let value = try await center.withLoading(message: "提交中") {
+            XCTAssertEqual(center.snapshotForTests, GlobalLoadingSnapshot(isVisible: true, message: "提交中", activeCount: 1))
+            return 42
+        }
+
+        XCTAssertEqual(value, 42)
+        XCTAssertEqual(center.snapshotForTests, GlobalLoadingSnapshot(isVisible: false, message: "", activeCount: 0))
+    }
+
+    /// 测试 withLoading 抛错时也会自动隐藏 Loading。
+    func testWithLoadingHidesAfterFailure() async {
+        let center = GlobalLoadingCenter()
+
+        do {
+            _ = try await center.withLoading(message: "提交中") {
+                throw TestFailure.expected
+            } as Int
+            XCTFail("withLoading 应该向外抛出业务错误")
+        } catch {
+            XCTAssertEqual(error as? TestFailure, .expected)
+        }
+
+        XCTAssertEqual(center.snapshotForTests, GlobalLoadingSnapshot(isVisible: false, message: "", activeCount: 0))
+    }
+
+    /// 测试 withOptionalLoading 关闭时不会改变展示状态。
+    func testWithOptionalLoadingDisabledDoesNotChangeState() async throws {
+        let center = GlobalLoadingCenter()
+
+        let value = try await center.withOptionalLoading(false, message: "不展示") {
+            XCTAssertEqual(center.snapshotForTests, GlobalLoadingSnapshot(isVisible: false, message: "", activeCount: 0))
+            return "done"
+        }
+
+        XCTAssertEqual(value, "done")
+        XCTAssertEqual(center.snapshotForTests, GlobalLoadingSnapshot(isVisible: false, message: "", activeCount: 0))
+    }
+
+    /// 测试使用 Loading 不需要读取可观察展示状态，业务侧只能拿到命令中心类型。
+    func testBusinessCodeOnlyDependsOnCommandCenter() {
+        let center = GlobalLoadingCenter()
+
+        issueLoadingCommand(center)
+
+        XCTAssertEqual(center.snapshotForTests, GlobalLoadingSnapshot(isVisible: true, message: "加载中", activeCount: 1))
+        center.hide()
+    }
+
+    /// 模拟业务代码只接收命令中心并发出展示指令。
+    private func issueLoadingCommand(_ center: GlobalLoadingCenter) {
+        center.show(message: "加载中")
+    }
+
+    /// 测试用错误类型。
+    private enum TestFailure: Error, Equatable {
+        case expected
+    }
+}