fix: sync Quick Prompt popup theme with main app

The popup window has its own document and never received the
data-theme attribute. Pass the current theme setting from the main
process via the show event, resolve 'system' to effective dark/light,
and apply to document.documentElement.dataset.theme so all CSS
variables match the main app's appearance.

- Add getCurrentTheme() to AryxAppService
- Pass theme in toggleQuickPromptWindow / showQuickPromptWindow
- Update onShow listener signature to receive theme string
- Apply theme to documentElement on each popup activation

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

src/main/index.ts

@@ -83,7 +83,7 @@ async function bootstrap(): Promise<void> {
       const hotkeySettings = workspace.settings.quickPrompt ?? createDefaultQuickPromptSettings();
       globalHotkeyService.register(hotkeySettings, () => {
         const win = ensureQuickPromptWindow();
-        if (win) void toggleQuickPromptWindow(win);
+        if (win) void toggleQuickPromptWindow(win, appService!.getCurrentTheme());
       });
 
       // Re-register hotkey when settings change