[Job Launcher] Remove fundAmount from fortune manifest

[flopez7]

** Description**
Stop relying on fundAmount inside manifest and move the source of truth to on-chain/subgraph data.

** Motivation **
fundAmount is currently duplicated between the manifest and the escrow/job state. Removing it from the manifest would reduce coupling and make the manifest and job creation simpler

** Implementation details**

• Update Job Launcher to remove fundAmount from the manifest.
• Review the other oracles and replace current manifest-based fundAmount usage with data from the subgraph.
• Adjust reward and completion logic accordingly.