- Added optional 'topic' field to BipolarTriggerRequest model
- Added topic parameter to force_trigger_argument and force_trigger_argument_from_message_id
- Updated run_argument to accept optional custom topic (None=random, ''=no topic, str=custom)
- Added topic input field to Web UI trigger-argument section
- Updated JS to send topic in API request body
- Custom topics bypass the random rotation system, allowing manual theme control