Customer API-key governance

Separate customer access from node telemetry access.

Node keys authenticate infrastructure. Customer API keys authenticate inference customers, enforce quotas, and bind workloads to allowed regions.

Name	Prefix	Allowed regions	Quota	Status
Production inference key	`ue_live_prod_8f2`	APAC, EU	25M tokens/month	active
Sandbox integration key	`ue_test_sbx_3c1`	Global non-sensitive	1M tokens/month	active
Legacy pilot key	`ue_live_old_9aa`	Africa	5M tokens/month	rotation required