Serialized execution witness proving service

Add a long-running process that accepts a serialized [ExecutionWitness](https://github.com/0xMiden/miden-vm/blob/18d9f6361acbf2f8fb22e4780b312e4b4f96cbce/processor/src/trace/mod.rs#L61-L134) and returns an `ExecutionProof`. The first version needs one request transport and a single service process.

The issue is complete when:

- the service handles more than one request without restarting.
- it checks the request version and size before proving.
- untrusted requests use the safe reader tracked by [#3303](https://github.com/0xMiden/miden-vm/issues/3303).
- a bounded queue limits concurrent proof jobs.
- each job uses the VM and precompile prover limits.
- shutdown or client cancellation stops queued work.
- responses contain either an `ExecutionProof` or a stable error code.

Add an integration test for a valid request. Add rejection tests for malformed and oversized requests.