#970 Split 8 code files over the 550-line cap that #855-#904 do not cover

EARS: Each tracked code file shall be at most 550 lines. Found by the #918 size gate (git ls-files --recurse-submodules, .py/.sh/.js/.ts/.svelte/.sql, migrations excluded) at superproject 1d2cf22 / core 263d9da / jumper 695c8ad: api/tests/test_rbac_permissions.py 1137, tests/helpers/api_client.py 873, tests/integration/test_atomicity_baseline.py 732, tests/unit/db/test_connection_pool_stress.py 588, tests/wip_integration/test_durable_cron.py 582, docker/highway-core/engine/sql/queries/apps.sql 600, docker/highway-core/lib/jumper/demo_distributed.py 759, docker/highway-core/lib/jumper/tests/test_jumper_client.py 725. They sit in scripts/ci/size_allowlist.json at their exact size; the gate fails if one grows, and fails until its entry is lowered or removed when it shrinks. Only enterprise/apps/pre_installed/example_app.py (661, #888 wont-do) is covered by the existing tickets; every other #855-#904 file is already under the cap.