fix: HTML-escape IRC username in Owncast chat, fix WebSocket auth, fix echo suppression

- Escape angle brackets around IRC username so Owncast doesn't swallow
  them as HTML tags (&lt;nick&gt; instead of <nick>)
- Register a chat user via POST /api/chat/register to obtain an
  accessToken, then pass it as a query param when connecting to /ws
  (Owncast closes the WebSocket immediately without one)
- Cache the access token across reconnections; re-register only on
  rejection
- Add ws_display_name config option (default "IRC Bridge")
- Fix echo suppression: record_sent and is_echo now both compare
  raw body instead of mismatched formatted/raw values

Made-with: Cursor

config.example.toml

@@ -11,6 +11,7 @@ url = "https://owncast.bowlafterbowl.com"
 webhook_port = 9078
 websocket_enabled = true
 health_poll_interval_secs = 30
+ws_display_name = "IRC Bridge"
 
 [bridge]
 irc_prefix = "[IRC]"