fix(appearance): 完善深色模式和阅读页面对比度

- 区分按钮填充与图标颜色，统一书架、书源、搜索和阅读设置的选中态
- 调整编辑器语法高亮、键盘工具栏及统计卡片的浅深色显示
- 适配 RSS 正文和登录网页背景，保留书源自定义样式和页面状态
- 补充外观切换、页面对比度和管理页面的回归测试

Tests/LegadoReaderTests/WebReaderBridgeTests.swift

@@ -5,6 +5,56 @@ import XCTest
 
 @MainActor
 final class WebReaderBridgeTests: XCTestCase {
+    func testGeneratedRSSContentFollowsAppearanceWithoutReloading() async throws {
+        let source = RssSource(sourceUrl: "https://appearance-regression.test", sourceName: "测试")
+        let loaded = expectation(description: "HTML loaded")
+        let surface = RSSWebReaderView(
+            mode: .html(content: "<body><p>订阅正文</p><a href='#'>链接</a><button>操作</button></body>", baseURL: nil),
+            source: source, onTextChange: { _ in loaded.fulfill() }
+        )
+        let coordinator = surface.makeCoordinator()
+        let webView = WKWebView(frame: CGRect(x: 0, y: 0, width: 390, height: 844))
+        webView.navigationDelegate = coordinator
+        let window = UIWindow(frame: webView.frame)
+        let controller = UIViewController()
+        controller.overrideUserInterfaceStyle = .dark
+        controller.view.addSubview(webView)
+        window.rootViewController = controller
+        window.makeKeyAndVisible()
+        defer {
+            RSSWebReaderView.dismantleUIView(webView, coordinator: coordinator)
+            window.isHidden = true
+        }
+        coordinator.installRulesAndLoad(mode: surface.mode, in: webView)
+        await fulfillment(of: [loaded], timeout: 20)
+        let appearanceScript = """
+        [matchMedia('(prefers-color-scheme:dark)').matches,
+         getComputedStyle(document.body).backgroundColor,
+         getComputedStyle(document.body).color,
+         getComputedStyle(document.querySelector('a')).color,
+         getComputedStyle(document.documentElement).colorScheme].map(String).join('|')
+        """
+        let dark = try await webView.evaluateJavaScript(appearanceScript)
+        XCTAssertEqual(dark as? String, "true|rgb(17, 17, 19)|rgb(242, 242, 242)|rgb(158, 203, 255)|light dark")
+        _ = try await webView.evaluateJavaScript("window.appearanceMarker = 'preserved'")
+        controller.overrideUserInterfaceStyle = .light
+        window.layoutIfNeeded()
+        XCTAssertEqual(webView.traitCollection.userInterfaceStyle, .light)
+        var light = try await webView.evaluateJavaScript(appearanceScript)
+        for _ in 0..<50 {
+            if (light as? String)?.hasPrefix("false|") == true { break }
+            try await Task.sleep(nanoseconds: 100_000_000)
+            light = try await webView.evaluateJavaScript(appearanceScript)
+        }
+        XCTAssertEqual(light as? String, "false|rgb(252, 252, 252)|rgb(23, 23, 23)|rgb(0, 0, 238)|light dark")
+        let marker = try await webView.evaluateJavaScript("window.appearanceMarker")
+        XCTAssertEqual(marker as? String, "preserved")
+        // A source may intentionally override the generated article palette.
+        _ = try await webView.evaluateJavaScript("document.head.insertAdjacentHTML('beforeend', '<style>body{color:rgb(120,30,40)}</style>')")
+        let custom = try await webView.evaluateJavaScript("getComputedStyle(document.body).color")
+        XCTAssertEqual(custom as? String, "rgb(120, 30, 40)")
+    }
+
     func testPageJavaScriptCanStoreVariablesAndEvaluateContentRules() async throws {
         let source = RssSource(sourceUrl: "https://bridge-regression.test/\(UUID().uuidString)", sourceName: "测试")
         let loaded = expectation(description: "HTML loaded")