Remove the pensieve management backend

[francoisferrand]

The pensieve backend implemented the Zenko 1.x Orbit flow: read the configuration overlay from the PENSIEVE metadata bucket, decrypt the secrets and patch the location constraints into the running config. Nobody deploys Backbeat that way anymore — zenko-operator always sets MANAGEMENT_BACKEND=operator, so the operator backend is the only one in use. MANAGEMENT_BACKEND is now simply ignored.

Beyond being dead code, patchConfiguration.js pulled in arsenal.patches.locationConstraints.patchLocations at load time in every Backbeat process, which kept Arsenal from dropping its pensieve helpers (ARSN-653). patchConfiguration.js now only keeps the ingestion bucket refresh used by the operator backend.

Also drops the now-unused convertServiceStateFormat, the PENSIEVE test fixtures and the MANAGEMENT_BACKEND mentions in docs/CI.

Related: CLDSRV-1013 (same cleanup in CloudServer).

Issue: BB-896

[bert-e]

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[bert-e]

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[claude]

Only the deleted pensieveBackend.js read REMOTE_MANAGEMENT_DISABLE, so it does nothing in Backbeat now (you also took it out of docs/configuration.md). Drop it here too. Other places still set it for Backbeat: README.md, docs/run-transition-locally.md, docs/run-crr-replay-locally.md and .github/dockerfiles/ft/docker-compose.yaml.

Suggested change

	REMOTE_MANAGEMENT_DISABLE=true yarn start
	yarn start