feat: Add automated profit withdrawal system
- UI page: /withdrawals with stats dashboard and config form
- Settings API: GET/POST for .env configuration
- Stats API: Real-time profit and withdrawal calculations
- Execute API: Safe withdrawal with Drift SDK integration
- Drift service: withdrawFromDrift() with USDC spot market (index 0)
- Safety checks: Min withdrawal amount, min account balance, profit-only
- Telegram notifications: Withdrawal alerts with Solscan links
- Dashboard navigation: Added Withdrawals card (3-card grid)
User goal: 10% of profits automatically withdrawn on schedule
Current: Manual trigger ready, scheduled automation pending
Files: 5 new (withdrawals page, 3 APIs, Drift service), 2 modified
ca7b49f745