Loading valves at startup does not update pipeline headers

[Aman-14]

When loading valves from the valves.json file, the pipeline headers are not updated as expected. Instead, the pipeline.valves are simply assigned without reflecting the changes in the pipeline headers.

Relevant code: main.py, lines 204-53

To resolve this, I believe you need to call await pipeline.on_valves_updated() after loading the valves to ensure the headers are properly set.

[Aman-14]

I can write a fix for this. Let me know when it's good to go.