[Job Launcher] Introduce new job creation endpoints

[flopez7]

Description
Add the new job creation API with two supported create flows:

• one endpoint for manifest_url + manifest_hash
• one endpoint that accepts the manifest directly in the request body as JSON

Motivation
This makes job creation easier to integrate and moves the API toward a more generic manifest-based model.

Implementation details

• Reuse the quick-launch flow for the URL/hash endpoint.
• Add a second create endpoint that accepts the manifest in the body together with the existing create parameters.
• Validate the manifest based on request_type by checking that the required properties are present, without changing the existing manifest shapes.
• Update JL client with the new logic