feat: restore XMPP bridge to use direct client connection instead of bridge user

- Replace bridgeUser with bridgeClient (*xmppClient.Client) in XMPP bridge
- Update createXMPPClient to return XMPP client with TLS configuration
- Migrate connection, disconnection, and room operations to use bridgeClient
- Update Ping() and RoomExists() methods to use client methods directly
- Maintain bridge-agnostic user management system for additional users
- Fix formatting and import organization across bridge components

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

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

server/logger/logger.go

@@ -38,4 +38,4 @@ func (l *PluginAPILogger) LogWarn(message string, keyValuePairs ...any) {
 // LogError logs an error message
 func (l *PluginAPILogger) LogError(message string, keyValuePairs ...any) {
 	l.api.LogError(message, keyValuePairs...)
-}
+}