feat(desktop): gate traffic-lights behind window-controls style setting

Add a Window controls Style setting ('classic' | 'traffic-lights',
default 'classic') next to the existing Position setting. All four
position×style combinations render correctly with side-driven order
(close,min,max left; min,max,close right).

- Restore deleted left-classic branch (h-8 w-8 rounded-md buttons)
- Add right-traffic-lights branch (cluster with ml-1 container)
- Branch on style instead of side in WindowsWindowControls
- Store field + setter with 'classic' default (no migration needed;
  Zustand persist shallow-merges over initial state)
- Settings UI: SettingsTwoColumn with Position chips + Style dropdown
- Sanitize on client (persistence.ts) and server (settings-helpers.js)
- 10 locale dictionaries updated (add-only, no existing keys changed)
- Traffic-light button spacing 8px→10px edge-to-edge
- Delete dead DESKTOP_WINDOW_CONTROLS_WIDTH_PX constant

packages/ui/src/lib/settings/search.ts

@@ -399,9 +399,9 @@ const SETTINGS_SEARCH_ITEMS: readonly SettingsSearchItem[] = [
   {
     id: 'sessions.desktop-window-controls-position',
     page: 'appearance',
-    titleKey: 'settings.openchamber.desktopNetwork.field.windowControls',
-    descriptionKey: 'settings.openchamber.desktopNetwork.field.windowControlsDescription',
-    keywords: ['desktop', 'window', 'controls', 'minimize', 'maximize', 'close', 'titlebar', 'linux', 'windows', 'position'],
+    titleKey: 'settings.openchamber.desktopNetwork.field.windowControlsPosition',
+    descriptionKey: 'settings.openchamber.desktopNetwork.field.windowControlsPositionDescription',
+    keywords: ['desktop', 'window', 'controls', 'minimize', 'maximize', 'close', 'titlebar', 'linux', 'windows'],
     isAvailable: (ctx) => ctx.isDesktop && (ctx.isWindows || !ctx.isMac),
   },
   {