Replace Yahoo Finance with Polygon.io for chart data

- Add Polygon.io API client for reliable historical data access
- Update bot to use Polygon instead of Yahoo Finance for charts
- Add POLYGON_API_KEY to config and environment example
- Polygon free tier: 5 API calls/minute, more reliable than Yahoo
- Fallback to FinViz chart URL when Polygon unavailable

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

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

test_polygon.py

@@ -0,0 +1,69 @@
+"""Test script for Polygon.io API integration."""
+import logging
+from polygon_api import PolygonAPI
+from chart_generator import ChartGenerator
+import os
+from dotenv import load_dotenv
+
+load_dotenv()
+
+logging.basicConfig(
+    level=logging.INFO,
+    format='%(asctime)s - %(name)s - %(levelname)s - %(message)s'
+)
+logger = logging.getLogger(__name__)
+
+
+def test_polygon_integration():
+    """Test Polygon.io API and chart generation."""
+
+    api_key = os.getenv('POLYGON_API_KEY')
+    if not api_key:
+        logger.error("POLYGON_API_KEY not set in .env file")
+        return False
+
+    logger.info("Initializing Polygon API")
+    api = PolygonAPI(api_key)
+
+    # Test tickers
+    tickers = ["AAPL", "TSLA"]
+
+    for ticker in tickers:
+        logger.info(f"\nTesting {ticker}...")
+
+        # Fetch candle data
+        logger.info(f"Fetching candle data for {ticker}")
+        candle_data = api.get_candles(ticker, days=30)
+
+        if not candle_data:
+            logger.error(f"Failed to fetch candle data for {ticker}")
+            continue
+
+        logger.info(f"Successfully fetched {len(candle_data['timestamps'])} candles")
+        logger.info(f"Price range: ${min(candle_data['low']):.2f} - ${max(candle_data['high']):.2f}")
+
+        # Generate chart
+        logger.info(f"Generating chart for {ticker}")
+        chart = ChartGenerator.create_price_chart(ticker, candle_data, f"{ticker} Test")
+
+        if not chart:
+            logger.error(f"Failed to generate chart for {ticker}")
+            continue
+
+        # Save chart
+        filename = f"/tmp/{ticker}_polygon_chart.png"
+        with open(filename, "wb") as f:
+            f.write(chart.getvalue())
+        logger.info(f"Chart saved: {filename} ({len(chart.getvalue())} bytes)")
+
+    logger.info("\nPolygon.io integration test completed successfully!")
+    return True
+
+
+if __name__ == "__main__":
+    try:
+        success = test_polygon_integration()
+        exit(0 if success else 1)
+    except Exception as e:
+        logger.error(f"Test failed: {e}", exc_info=True)
+        exit(1)