Potential fix for code scanning alert no. 1: Information exposure through an exception

[Exohayvan]

Potential fix for https://github.com/AetherMesh-AI/aethermesh-core/security/code-scanning/1

The best fix is to stop returning str(exc) in the submission response and replace it with a stable, generic message, while logging the exception server-side for diagnostics.

Concretely, in src/aethermesh_core/runtime_service.py within submit_local_job_status (around lines 864–872), update the except RuntimeServiceError as exc block to:

• log the exception with logger.exception(...) (or equivalent),
• return _submission_status(...) with a non-sensitive static message such as "Local submission request is invalid.".

This preserves existing functionality (request still returns a structured rejected status) but removes information exposure.
To implement this, runtime_service.py needs a module logger:

• add import logging with existing imports,
• define logger = logging.getLogger(__name__) near constants/import region.

No API signature changes are required.

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