fix: avoid socket client bare excepts

[jmolz]

Issue #, if available:
Refs #783

Description of changes:

• Replace the remaining bare except: handlers in trustgraph-base/trustgraph/api/socket_client.py with except Exception:.
• Import ConnectionClosed directly so the reader's connection-close handler is stable when handling reader errors.
• Add unit coverage to ensure socket-client cleanup paths no longer suppress process-level interrupts.

Testing:

• PYTHONPATH=trustgraph-base pytest tests/unit/test_python_api_client.py::TestSocketClient -q
• PYTHONPATH=trustgraph-base pytest tests/unit/test_python_api_client.py -q
• git diff --check
• rg -n "except\\s*:" trustgraph-base/trustgraph/api/socket_client.py
• python3 -m py_compile trustgraph-base/trustgraph/api/socket_client.py tests/unit/test_python_api_client.py

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[cybermaggedon]

Thanks for the PR, nice test too!