feat: Add powerful CLI for account management (#115)

* feat: Add powerful CLI for account management

- 18 commands for quota monitoring, switching, validation
- Interactive mode with keyboard navigation
- Smart auto-switch based on quotas
- Alias support for quick access
- Token auto-refresh and diagnostics
- Full documentation in cli/README.md"

* fix: Address code review issues - Add SQLite transactions for atomicity\n- Add input validation for import_accounts\n- Add per-account error handling in bulk operations\n- Add graceful error handling in interactive mode\n- Add validation for varint encoding (negative values)\n- Improve user feedback on partial failures

cli/PR_SUMMARY.md

@@ -0,0 +1,102 @@
+# CLI Feature - Pull Request Summary
+
+## What This PR Adds
+
+A complete **Command-Line Interface (CLI)** for Antigravity Manager with 18+ commands for power users.
+
+## Key Features
+
+- 📊 **Live Quota Monitoring** - Real-time tracking for Gemini & Claude models
+- 🔄 **Account Switching** - Seamless switching without manual token management  
+- ✅ **Token Validation** - Auto-refresh expired tokens
+- 🎯 **Smart Auto-Switch** - Automatically pick best account by quota
+- 🏷️ **Aliases** - Shortcut names for accounts (`work`, `personal`)
+- 💾 **Backup/Restore** - Export/import account configurations
+- 🎮 **Interactive Mode** - Keyboard-navigated menus for beginners
+- 🩺 **Diagnostics** - System health checks
+
+## Technical Highlights
+
+- **Zero Hardcoded Paths**: Intelligently discovers database and executable locations
+- **Cross-Platform Ready**: Uses environment variables and checks for Windows/Mac/Linux
+- **Secure**: Leverages existing DPAPI + AES-256-GCM encryption (same as GUI)
+- **Extensible**: Clean separation between core logic (`core.py`) and commands (`main.py`)
+
+## File Structure
+
+```
+cli/
+├── README.md           # Full documentation
+├── requirements.txt    # Python dependencies
+├── core.py            # Database, encryption, API logic
+├── main.py            # CLI commands and interactive UI
+└── proto_utils.py     # Protobuf encoding helpers
+```
+
+## Usage Examples
+
+```powershell
+# Interactive mode
+agm
+
+# Quick status
+agm status
+
+# Switch accounts
+agm switch work
+
+# Auto-switch to best account
+agm auto-switch --model claude --min-quota 50
+
+# Live monitoring
+agm watch
+```
+
+## Testing
+
+- ✅ Tested on Windows 10/11
+- ✅ No hardcoded paths (uses standard Windows env vars)
+- ✅ Works with both installed and development builds
+- ✅ Database encryption/decryption verified
+
+## Dependencies
+
+All Python dependencies are self-contained in `cli/requirements.txt`:
+- `typer` - CLI framework
+- `rich` - Beautiful terminal output
+- `questionary` - Interactive menus
+- `pywin32` - Windows DPAPI support
+- `cryptography` - AES-256-GCM encryption
+- `httpx` - Async HTTP client
+- `psutil` - Process management
+- `protobuf` - Google API protocol buffers
+
+## Platform Support
+
+- **Windows**: Full support (tested)
+- **macOS/Linux**: Partial support (no DPAPI, but core features work)
+
+## Breaking Changes
+
+None. This is a pure addition—no changes to existing GUI code.
+
+## Future Enhancements
+
+- OAuth flow for adding new accounts via CLI
+- TUI (Terminal UI) with live dashboard
+- Scheduled auto-refresh via Windows Task Scheduler
+- Config file for user preferences
+
+## Checklist
+
+- [x] Code follows existing style
+- [x] All commands have help text
+- [x] No hardcoded paths/credentials
+- [x] README with examples
+- [x] Dependencies in requirements.txt
+- [x] .gitignore updated for Python
+- [x] Works with fresh installs
+
+---
+
+**Ready to merge!** 🚀