chore: set `Dockerfile` to use Python 3.12 (#2230) #5474

Job	Run time
run-core-unit-tests (test_client.py)	3m 33s
run-core-unit-tests (test_local_client.py)	14m 38s
run-core-unit-tests (test_client_legacy.py)	15m 14s
run-core-unit-tests (test_server.py)	3m 38s
run-core-unit-tests (test_managers.py)	57s
run-core-unit-tests (test_o1_agent.py)	1m 42s
run-core-unit-tests (test_tool_rule_solver.py)	45s
run-core-unit-tests (test_agent_tool_graph.py)	2m 46s
run-core-unit-tests (test_utils.py)	46s
run-core-unit-tests (test_tool_schema_parsing.py)	6m 13s
run-core-unit-tests (test_v1_routes.py)	46s
run-core-unit-tests (test_offline_memory_agent.py)	2m 35s
misc-unit-tests	0s
	53m 33s

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