Switch to candlestick charts with 30-day daily data

- Replace line charts with candlestick charts for better visualization
- Green candles for up days, red for down days
- Daily resolution (30 days) - free tier compatible
- Auto-detect intraday vs daily data for proper time/date formatting
- Note: 5-min intraday requires paid Polygon tier ($199/month)

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

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

bot.py

@@ -263,12 +263,12 @@ class StockBot(commands.Bot):
             await channel.send(f"Unable to retrieve data for ticker: {ticker}")
             return
 
-        # Generate chart using Polygon.io historical data
+        # Generate chart using Polygon.io historical data (daily candlesticks)
         chart_file = None
         if self.chart_api:
-            candle_data = self.chart_api.get_candles(ticker, days=30)
+            candle_data = self.chart_api.get_candles(ticker, days=30, resolution='D')
             if candle_data:
-                chart_buffer = ChartGenerator.create_price_chart(
+                chart_buffer = ChartGenerator.create_candlestick_chart(
                     ticker,
                     candle_data,
                     stock_data.get('company_name')
@@ -559,12 +559,12 @@ async def get_stock_price(ctx, ticker: str = None):
         await ctx.send(f"Unable to retrieve data for ticker: {ticker}")
         return
 
-    # Generate chart using Polygon.io historical data
+    # Generate chart using Polygon.io historical data (daily candlesticks)
     chart_file = None
     if bot.chart_api:
-        candle_data = bot.chart_api.get_candles(ticker, days=30)
+        candle_data = bot.chart_api.get_candles(ticker, days=30, resolution='D')
         if candle_data:
-            chart_buffer = ChartGenerator.create_price_chart(
+            chart_buffer = ChartGenerator.create_candlestick_chart(
                 ticker,
                 candle_data,
                 stock_data.get('company_name')