feat: add optional custom argument topic override via Web UI

- 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

bot/routes/models.py

@@ -46,6 +46,7 @@ class BipolarTriggerRequest(BaseModel):
     channel_id: str  # String to handle large Discord IDs from JS
     message_id: str = None  # Optional: starting message ID (string)
     context: str = ""
+    topic: str = ""  # Optional: custom argument topic (overrides random topic selection)
 
 
 class ManualCropRequest(BaseModel):