feat: add token auth, new tools, and bug fixes

- Add Personal Access Token authentication (--auth-token/--user-id)
- Add --no-verify-ssl flag for self-signed certificates
- Add send_direct_message tool
- Add delete_message tool
- Add get_unread tool using subscriptions.get API
- Add send_file tool with @username auto-resolution via im.create
- Add DM listing to list_all_rooms
- Fix timestamp parsing (ISO string instead of $date object)
- Fix get_channel_messages to support channels/groups/im with fallback
- Include msgId in message output for delete operations
- Return msgId and roomId from send functions

Author: millerchou