Add dedicated channel for startup announcements

Add STARTUP_ANNOUNCEMENT_CHANNEL_ID to control where startup announcements are sent.

Changes:
- New config: STARTUP_ANNOUNCEMENT_CHANNEL_ID
- Announcements sent only to specified channel
- Falls back to first CHANNEL_ID if not set
- Prevents announcement spam in all stock update channels

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

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

README.md

@@ -161,6 +161,7 @@ Environment variables in `.env`:
 | `DISCORD_TOKEN` | Your Discord bot token | Required |
 | `CHANNEL_ID` | Discord channel ID(s) for updates (comma-separated for multiple) | Required |
 | `STARTUP_ANNOUNCEMENT` | Optional message to send when bot starts (empty = no announcement) | `""` |
+| `STARTUP_ANNOUNCEMENT_CHANNEL_ID` | Channel ID for startup announcements (defaults to first CHANNEL_ID) | `""` |
 | `COMMAND_PREFIX` | Command prefix for bot | `!` |
 | `PRIMARY_TICKER` | Stock ticker for hourly updates | `PYPL` |
 | `UPDATE_INTERVAL_HOURS` | Hours between updates | `1` |
@@ -173,7 +174,9 @@ CHANNEL_ID=1442203998932304035,9876543210123456789
 **Startup Announcements:** Send a one-time message when the bot starts (useful for announcing updates):
 ```
 STARTUP_ANNOUNCEMENT=Bot updated with new features: colored price changes and FinViz charts!
+STARTUP_ANNOUNCEMENT_CHANNEL_ID=1234567890123456789
 ```
+If `STARTUP_ANNOUNCEMENT_CHANNEL_ID` is not set, announcements are sent to the first channel in `CHANNEL_ID`.
 
 ## Switching Stock API Providers