Add US session zones, check-for-updates, UI polish

- StockChartView: mark 盘前/盘中/盘后 with colored background zones and text labels for US stocks
- UpdateChecker: check latest release via GitHub API, prompt user to download if newer version found; semantic version comparison to avoid false positives
- SettingsView: add 关于 section with version and 检查更新 button; hide scrollbar (.never)
- DropdownView: hide scrollbar (.never)
- ProfitSummaryView: replace opaque white background with subtle transparent tint
- project.pbxproj: normalize MARKETING_VERSION to 1.0.0 (three-part semver)
- README/README_CN: add main screenshot

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

StockMonitor/Services/UpdateChecker.swift

@@ -0,0 +1,80 @@
+import Foundation
+import AppKit
+import Combine
+
+private struct GitHubRelease: Decodable {
+    let tagName: String
+    let htmlUrl: String
+    enum CodingKeys: String, CodingKey {
+        case tagName = "tag_name"
+        case htmlUrl = "html_url"
+    }
+}
+
+@MainActor
+final class UpdateChecker: ObservableObject {
+
+    static let shared = UpdateChecker()
+    private init() {}
+
+    @Published var isChecking = false
+
+    func checkForUpdates() {
+        guard !isChecking else { return }
+        isChecking = true
+        Task { await run() }
+    }
+
+    private func run() async {
+        defer { isChecking = false }
+
+        guard let url = URL(string: "https://api.github.com/repos/VGEAREN/Stockbar/releases/latest") else { return }
+        var req = URLRequest(url: url)
+        req.setValue("application/vnd.github+json", forHTTPHeaderField: "Accept")
+
+        guard let (data, _) = try? await URLSession.shared.data(for: req),
+              let release = try? JSONDecoder().decode(GitHubRelease.self, from: data) else {
+            alert(title: "检查失败", body: "无法获取版本信息，请检查网络连接。")
+            return
+        }
+
+        let latestTag = release.tagName
+        let latest  = latestTag.hasPrefix("v") ? String(latestTag.dropFirst()) : latestTag
+        let current = Bundle.main.infoDictionary?["CFBundleShortVersionString"] as? String ?? "0"
+
+        if isNewer(latest, than: current) {
+            let a = NSAlert()
+            a.messageText    = "发现新版本 \(latest)"
+            a.informativeText = "当前版本 \(current)。下载 DMG 后将旧版本替换即可完成更新。"
+            a.addButton(withTitle: "前往下载")
+            a.addButton(withTitle: "暂不更新")
+            if a.runModal() == .alertFirstButtonReturn,
+               let releaseURL = URL(string: release.htmlUrl) {
+                NSWorkspace.shared.open(releaseURL)
+            }
+        } else {
+            alert(title: "已是最新版本", body: "当前版本 \(current) 已是最新。")
+        }
+    }
+
+    /// 逐段比较语义版本，"1.0" 与 "1.0.0" 视为相等，不误报
+    private func isNewer(_ remote: String, than local: String) -> Bool {
+        let r = remote.split(separator: ".").compactMap { Int($0) }
+        let l = local.split(separator: ".").compactMap  { Int($0) }
+        let len = max(r.count, l.count)
+        for i in 0..<len {
+            let rv = i < r.count ? r[i] : 0
+            let lv = i < l.count ? l[i] : 0
+            if rv != lv { return rv > lv }
+        }
+        return false
+    }
+
+    private func alert(title: String, body: String) {
+        let a = NSAlert()
+        a.messageText     = title
+        a.informativeText = body
+        a.addButton(withTitle: "好")
+        a.runModal()
+    }
+}

StockMonitor/Views/DropdownView.swift

@@ -45,6 +45,7 @@ struct DropdownView: View {
                         }
                         .padding(.horizontal, 6)
                     }
+                    .scrollIndicators(.never)
                     .frame(maxHeight: 520)
                 }
 

StockMonitor/Views/ProfitSummaryView.swift

@@ -35,7 +35,7 @@ struct ProfitSummaryView: View {
             }
             .padding(.horizontal, 8)
             .padding(.vertical, 5)
-            .background(Color(nsColor: .controlBackgroundColor))
+            .background(Color.primary.opacity(0.04))
             .cornerRadius(6)
         }
     }

StockMonitor/Views/SettingsView.swift

@@ -6,6 +6,8 @@ struct SettingsView: View {
     @EnvironmentObject var appState: AppState
     @Binding var showSettings: Bool
 
+    @ObservedObject private var updater = UpdateChecker.shared
+
     @State private var launchAtLogin = (SMAppService.mainApp.status == .enabled)
     @State private var searchText    = ""
     @State private var searchResults = [SearchResult]()
@@ -21,6 +23,7 @@ struct SettingsView: View {
     var body: some View {
         ScrollView {
             VStack(alignment: .leading, spacing: 12) {
+
                 if let s = editingStock {
                     inlineEditView(s)
                 } else {
@@ -93,6 +96,32 @@ struct SettingsView: View {
                         }
                 }
 
+                // 关于 & 更新
+                section("关于") {
+                    HStack {
+                        VStack(alignment: .leading, spacing: 2) {
+                            Text("Stockbar")
+                                .font(.system(size: 12, weight: .medium))
+                            Text("版本 \(Bundle.main.infoDictionary?["CFBundleShortVersionString"] as? String ?? "-")")
+                                .font(.caption)
+                                .foregroundColor(.secondary)
+                        }
+                        Spacer()
+                        Button {
+                            UpdateChecker.shared.checkForUpdates()
+                        } label: {
+                            if UpdateChecker.shared.isChecking {
+                                ProgressView().scaleEffect(0.6).frame(width: 60)
+                            } else {
+                                Text("检查更新")
+                            }
+                        }
+                        .buttonStyle(.borderedProminent)
+                        .controlSize(.small)
+                        .disabled(UpdateChecker.shared.isChecking)
+                    }
+                }
+
                 // 添加股票
                 section("添加股票") {
                     HStack {
@@ -136,6 +165,7 @@ struct SettingsView: View {
             }
             .padding(8)
         }
+        .scrollIndicators(.never)
         .frame(width: 284, height: 480)
     }
 

StockMonitor/Views/StockChartView.swift

@@ -106,6 +106,13 @@ struct StockChartView: View {
         }
     }
 
+    // 美股时段定义：x 轴 index（基准 04:00 ET，每分钟 +1）
+    private let usSessions: [(name: String, start: Int, end: Int, color: Color)] = [
+        ("盘前", 0,   329, Color.indigo),
+        ("盘中", 330, 719, Color.teal),
+        ("盘后", 720, 959, Color.orange),
+    ]
+
     private var lineChart: some View {
         let prices = points.map(\.price)
         let minP = prices.min() ?? preClose
@@ -120,8 +127,36 @@ struct StockChartView: View {
             : Color(appState.config.downColorName)
 
         let labelPositions = xAxisLabels.map(\.0)
+        let isUS = stock.market == .usStock
+        let labelY = yMin + (yMax - yMin) * 0.88
 
         return Chart {
+            // 美股时段背景色块
+            if isUS {
+                ForEach(usSessions, id: \.name) { s in
+                    RectangleMark(
+                        xStart: .value("xs", s.start),
+                        xEnd:   .value("xe", s.end),
+                        yStart: .value("ys", yMin),
+                        yEnd:   .value("ye", yMax)
+                    )
+                    .foregroundStyle(s.color.opacity(0.07))
+                }
+                // 美股时段文字标注
+                ForEach(usSessions, id: \.name) { s in
+                    PointMark(
+                        x: .value("t", (s.start + s.end) / 2),
+                        y: .value("price", labelY)
+                    )
+                    .symbolSize(0)
+                    .annotation(position: .overlay) {
+                        Text(s.name)
+                            .font(.system(size: 9, weight: .medium))
+                            .foregroundColor(s.color.opacity(0.65))
+                    }
+                }
+            }
+
             // 昨收参考线
             RuleMark(y: .value("昨收", preClose))
                 .lineStyle(StrokeStyle(lineWidth: 0.8, dash: [4, 4]))