Add matplotlib-based chart generation with Yahoo Finance data

- Add chart_generator.py with price and candlestick chart support
- Implement Yahoo Finance candle data fetching for free historical data
- Update bot to generate and attach charts to stock embeds
- Add matplotlib dependency to requirements.txt
- Configure dual API approach: Finnhub for quotes, Yahoo for charts

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

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

bot.py

@@ -10,6 +10,7 @@ from config import Config
 from stock_api import YahooFinanceAPI, FinnhubAPI
 from market_hours import MarketHours
 from crypto_api import CoinGeckoAPI
+from chart_generator import ChartGenerator
 
 
 # Configure logging
@@ -36,6 +37,10 @@ class StockBot(commands.Bot):
             self.stock_api = YahooFinanceAPI()
             logger.info("Using Yahoo Finance API for stock data")
 
+        # Always initialize Yahoo Finance for chart data (free historical data)
+        self.yahoo_api = YahooFinanceAPI()
+        logger.info("Using Yahoo Finance API for chart data")
+
         self.scheduler = AsyncIOScheduler(timezone=pytz.timezone('America/New_York'))
         self.target_channel_ids = [int(id) for id in Config.CHANNEL_IDS]
         self.primary_ticker = Config.PRIMARY_TICKER
@@ -254,7 +259,25 @@ class StockBot(commands.Bot):
             return
 
         embed = self.create_stock_embed(stock_data)
-        await channel.send(embed=embed)
+
+        # Generate chart using Yahoo Finance historical data
+        chart_file = None
+        candle_data = self.yahoo_api.get_candles(ticker, days=30)
+        if candle_data:
+            chart_buffer = ChartGenerator.create_price_chart(
+                ticker,
+                candle_data,
+                stock_data.get('company_name')
+            )
+            if chart_buffer:
+                chart_file = discord.File(chart_buffer, filename="chart.png")
+
+        # Send with chart attachment if available
+        if chart_file:
+            await channel.send(embed=embed, file=chart_file)
+        else:
+            await channel.send(embed=embed)
+
         logger.info(f"Sent stock update for {ticker} to channel {channel_id}")
 
     def create_stock_embed(self, stock_data: dict) -> discord.Embed:
@@ -310,9 +333,8 @@ class StockBot(commands.Bot):
         embed.add_field(name="Change", value=change_str, inline=True)
         embed.add_field(name="Previous Close", value=f"${stock_data['previous_close']}", inline=True)
 
-        # Add FinViz daily chart
-        chart_url = f"https://finviz.com/chart.ashx?t={ticker}&ty=c&ta=1&p=d&s=l"
-        embed.set_image(url=chart_url)
+        # Reference attached chart image
+        embed.set_image(url="attachment://chart.png")
 
         market_status = "🟢 Market Open" if stock_data['market_open'] else "🔴 Market Closed"
         embed.set_footer(text=f"{market_status}")
@@ -526,7 +548,24 @@ async def get_stock_price(ctx, ticker: str = None):
         return
 
     embed = bot.create_stock_embed(stock_data)
-    await ctx.send(embed=embed)
+
+    # Generate chart using Yahoo Finance historical data
+    chart_file = None
+    candle_data = bot.yahoo_api.get_candles(ticker, days=30)
+    if candle_data:
+        chart_buffer = ChartGenerator.create_price_chart(
+            ticker,
+            candle_data,
+            stock_data.get('company_name')
+        )
+        if chart_buffer:
+            chart_file = discord.File(chart_buffer, filename="chart.png")
+
+    # Send with chart attachment if available
+    if chart_file:
+        await ctx.send(embed=embed, file=chart_file)
+    else:
+        await ctx.send(embed=embed)
 
 
 @bot.command(name='crypto', aliases=['c'])