fix: sync title bar overlay colors with app theme

The Windows title bar overlay (minimize/maximize/close buttons) was
hardcoded to dark colors and did not update when switching themes.

- Add titleBarTheme helper that maps AppearanceTheme to overlay and
  background colors, using nativeTheme for the system preference
- Call applyTitleBarTheme from the setTheme IPC handler so the overlay
  updates immediately on theme change
- Apply persisted theme on startup so the overlay matches from launch

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

src/main/index.ts

@@ -3,6 +3,7 @@ import { app, BrowserWindow } from 'electron';
 import { registerIpcHandlers } from '@main/ipc/registerIpcHandlers';
 import { EryxAppService } from '@main/EryxAppService';
 import { createMainWindow } from '@main/windows/createMainWindow';
+import { applyTitleBarTheme } from '@main/windows/titleBarTheme';
 
 let mainWindow: BrowserWindow | undefined;
 let appService: EryxAppService | undefined;
@@ -13,6 +14,10 @@ async function bootstrap(): Promise<void> {
   mainWindow = createMainWindow();
   registerIpcHandlers(mainWindow, appService);
 
+  // Apply persisted theme to the title bar overlay
+  const workspace = await appService.loadWorkspace();
+  applyTitleBarTheme(mainWindow, workspace.settings.theme);
+
   if (!app.isPackaged) {
     mainWindow.webContents.openDevTools({ mode: 'detach' });
   }