feat: account management overhaul + 7 issue resolutions (#147)

- Add smart JSON export/import with schema validation and deduplication
- Add per-account proxy configurations (Issue #79)
- Add advanced account sorting engine (Issues #126 & #99)
- Add compact horizontal layout, AI credits, inline model visibility (Issues #145 & #134)
- Add desktop push notifications for low quota (Issue #53)
- Fix Arch Linux AUR process detection bug (Issue #117)
- Default theme set to Dark Mode (it's better)
- UI Polishing: Improved sort dropdown and symmetrical dialog layouts
- Dev Mode: Resolved port conflicts and single-instance locks
- Updated README and README.zh-CN with new features

src/main.ts

@@ -122,10 +122,17 @@ function showWindowsInstallNoticeIfNeeded() {
   });
 }
 
+const isDev = process.env.NODE_ENV === 'development' || !app.isPackaged;
+
+if (isDev) {
+  app.setName('Antigravity Manager Dev');
+}
+
 const gotSingleInstanceLock = app.requestSingleInstanceLock();
 
 if (!gotSingleInstanceLock) {
   app.quit();
+  process.exit(0);
 } else {
   app.on('second-instance', () => {
     logger.info('Second instance detected, focusing existing window');