Bump version to 1.6.0 and add changelog release section #28

Job	Run time
Static analysis (ruff + mypy)	50s
Python 3.10	19s
Python 3.11	18s
Python 3.12	21s
Conformance suite in sync	3s
Python 3.9	32s
Python 3.13	19s
Broker integration (Redis · RabbitMQ · SQS)	1m 17s
CI green	3s
Broker integration (Redis · RabbitMQ · SQS)	1m 19s
Conformance suite in sync	3s
Python 3.11	18s
Python 3.13	19s
Static analysis (ruff + mypy)	50s
Python 3.10	19s
Python 3.12	21s
Python 3.9	32s
CI green	2s
	8m 5s

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