feat(windows): Phase 6 C2 — close-to-tray + Settings toggle 持久化

- ui/settings-page.slint: SettingsToggleRow 的 toggled callback
  从 (bool) 改成 (string, bool) — 把 row 自己的 label + 新 value
  一起交给 caller；row 内部先 value=!value 再 emit；value 改
  in-out property 让内部可以 flip；SettingsPage 加 callback
  toggle-persist(string, bool)；7 个真 toggle 全部 wire 到
  toggle-persist（Notifications 4 + Startup 3）
- ui/app.slint: MainWindow 加 in-out property ×7 +
  setting-toggled(string, bool) callback；启动从 ActiveConfig
  装载；SettingsPage section 把 7 个 property forward 给 page +
  toggle-persist 转接到 root.setting-toggled
- src/lib.rs:
  · 启动从 ActiveConfig 读 7 个 toggle 设到 MainWindow
  · 新 on_setting_toggled 回调：load AppConfig → 按 label 改
    对应字段 → save_config；start_with_windows 额外调
    startup::set_enabled 写 HKCU Run（Phase 6 C1）
  · on_close_requested 看 close_to_tray：true 时
    window().hide() + KeepWindowShown；false 时保持原来的
    HideWindow 行为

避坑：
- Slint 1.x callback 不能直接用 label 区分，必须 caller 传
  string 参数；改造 (bool) → (string, bool)
- 设置 in-out property 让 row 内部能 flip value 然后 emit
  新值（caller 收到的就是 post-flip 值）
- close_to_tray 在 UI MainWindow 上是 in-out property，Rust
  端用 get_close_to_tray() 实时读，所以 toggle 立刻影响
  close_requested 行为（不需要重启）
- on_close_requested 内部读 get_close_to_tray 要 upgrade()
  MainWindow weak handle，捕获空时 fallback false（默认
  close 而不是 hide）

验证：cargo build / build --release 都 exit 0，0 warning
- cargo test: 15 passed; 0 failed
- debug   35.64 MB, subsystem = WINDOWS_CUI
- release  9.78 MB, subsystem = WINDOWS_GUI

ui/settings-page.slint

@@ -16,9 +16,14 @@ import { ServerCard } from "./server-card.slint";
 
 export component SettingsToggleRow inherits Rectangle {
     in property <string> label;
-    in property <bool> value: false;
+    // `in-out` so the TouchArea can flip it before emitting the
+    // toggled(label, new-value) event.
+    in-out property <bool> value: false;
     in property <bool> enabled: true;
-    callback toggled(bool);
+    // Phase 6 C2: pass the row's own label + the new value to the
+    // caller so a single callback on the page can dispatch to the
+    // right AppConfig field.
+    callback toggled(string, bool);
 
     in property <color> row-bg: #28292d;
     in property <color> row-border: #3a3b40;
@@ -66,7 +71,8 @@ export component SettingsToggleRow inherits Rectangle {
             TouchArea {
                 enabled: root.enabled;
                 clicked => {
-                    root.toggled(!root.value);
+                    root.value = !root.value;
+                    root.toggled(root.label, root.value);
                 }
             }
         }
@@ -123,13 +129,13 @@ export component SettingsPage inherits Rectangle {
     in-out property <int> appearance-index: 2;
     callback appearance-changed(int);
 
-    // Notifications (UI shell)
+    // Notifications (Phase 6 C2: live wired through setting-toggled)
     in-out property <bool> desktop-notify: true;
     in-out property <bool> sound: true;
     in-out property <bool> notify-high: true;
     in-out property <bool> notify-max: true;
 
-    // Startup (UI shell)
+    // Startup (Phase 6 C2: live wired)
     in-out property <bool> start-with-windows: false;
     in-out property <bool> start-minimized: false;
     in-out property <bool> close-to-tray: true;
@@ -141,6 +147,12 @@ export component SettingsPage inherits Rectangle {
     in-out property <bool> test-in-progress: false;
     callback test-connection-requested();
 
+    // Phase 6 C2: a single callback that covers every toggle row on
+    // this page. Rust receives `(label, new_value)` and routes to the
+    // correct AppConfig field (and, for "start_with_windows", to the
+    // HKCU Run registry).
+    callback toggle-persist(string, bool);
+
     // Tokens
     in property <color> divider-color: #3a3b40;
     in property <color> hint-color: #6a6a6a;
@@ -199,21 +211,37 @@ export component SettingsPage inherits Rectangle {
             SettingsToggleRow {
                 label: "Enable desktop notification";
                 value: root.desktop-notify;
+                toggled(l, v) => {
+                    root.desktop-notify = v;
+                    root.toggle-persist(l, v);
+                }
             }
             SettingsToggleRow {
                 label: "Play sound";
                 value: root.sound;
                 enabled: root.desktop-notify;
+                toggled(l, v) => {
+                    root.sound = v;
+                    root.toggle-persist(l, v);
+                }
             }
             SettingsToggleRow {
                 label: "Notify on High priority";
                 value: root.notify-high;
                 enabled: root.desktop-notify;
+                toggled(l, v) => {
+                    root.notify-high = v;
+                    root.toggle-persist(l, v);
+                }
             }
             SettingsToggleRow {
                 label: "Notify on Max priority";
                 value: root.notify-max;
                 enabled: root.desktop-notify;
+                toggled(l, v) => {
+                    root.notify-max = v;
+                    root.toggle-persist(l, v);
+                }
             }
         }
 
@@ -224,14 +252,26 @@ export component SettingsPage inherits Rectangle {
             SettingsToggleRow {
                 label: "Start with Windows";
                 value: root.start-with-windows;
+                toggled(l, v) => {
+                    root.start-with-windows = v;
+                    root.toggle-persist(l, v);
+                }
             }
             SettingsToggleRow {
                 label: "Start minimized to tray";
                 value: root.start-minimized;
+                toggled(l, v) => {
+                    root.start-minimized = v;
+                    root.toggle-persist(l, v);
+                }
             }
             SettingsToggleRow {
                 label: "Close button minimizes to tray";
                 value: root.close-to-tray;
+                toggled(l, v) => {
+                    root.close-to-tray = v;
+                    root.toggle-persist(l, v);
+                }
             }
         }