Change startup announcement title to 'Bot Restarted'

Update embed title from "Bot Update" to "Bot Restarted" for clearer messaging.

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

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

bot.py

@@ -106,7 +106,7 @@ class StockBot(commands.Bot):
     async def send_startup_announcement(self):
         """Send startup announcement to configured announcement channel."""
         embed = discord.Embed(
-            title="🤖 Bot Update",
+            title="🤖 Bot Restarted",
             description=Config.STARTUP_ANNOUNCEMENT,
             color=discord.Color.blue(),
             timestamp=datetime.now(pytz.timezone('America/New_York'))