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

README.md

@@ -158,7 +158,12 @@ When using Antigravity IDE, have you ever encountered these problems?
 - **🖥️ System Tray** - Background mode with tray icon and right-click menu
 - **🔗 IDE Sync** - Automatically scan and import accounts from IDE's `state.vscdb`
 - **📦 Batch Operations** - Batch refresh and delete multiple accounts
-- **🌏 Internationalization** - Multi-language support (English / 中文)
+- **📤 JSON Export/Import** - Export and import account pools with schema validation and deduplication
+- **🔔 Desktop Notifications** - Configurable alerts when model quota drops below your threshold
+- **🌐 Per-Account Proxy** - Route individual accounts through their own HTTP/SOCKS5 proxy
+- **📊 Smart Sorting** - Sort accounts by recently used, overall quota, or specific model groups
+- **📋 Compact Layout** - Dense horizontal view to maximize visible accounts
+- **🌏 Internationalization** - Multi-language support (English / 中文 / Русский)
 - **🎨 Modern UI** - Built with React, TailwindCSS, and Shadcn UI
 
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