Add earnings calendar feature with command and scheduled delivery

Implement comprehensive earnings calendar functionality that displays upcoming earnings for major companies (market cap > $10B). Feature includes both manual command access and automated weekly delivery.

Key additions:
- Finnhub API integration for earnings calendar data with market cap filtering
- Discord embed formatting grouped by day with EPS/revenue estimates
- !earnings command for manual queries (current or next week)
- Weekly scheduled task (Sunday 6PM ET) for automatic delivery
- Configuration options for market cap threshold and schedule timing

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

config.py

@@ -20,6 +20,11 @@ class Config:
     STOCK_API_PROVIDER = os.getenv('STOCK_API_PROVIDER', 'finnhub')  # 'yahoo' or 'finnhub'
     FINNHUB_API_KEY = os.getenv('FINNHUB_API_KEY')
 
+    # Earnings calendar configuration
+    EARNINGS_MIN_MARKET_CAP_BILLIONS = float(os.getenv('EARNINGS_MIN_MARKET_CAP_BILLIONS', '10'))
+    EARNINGS_SCHEDULE_DAY = os.getenv('EARNINGS_SCHEDULE_DAY', 'sun')
+    EARNINGS_SCHEDULE_HOUR = int(os.getenv('EARNINGS_SCHEDULE_HOUR', '18'))
+
     # Scheduling configuration
     UPDATE_INTERVAL_HOURS = int(os.getenv('UPDATE_INTERVAL_HOURS', '1'))