Add Plan Feature Flag for Epics Deployments

Deployments, Incidents and other things added by these Epics must be behind a standard Plan feature flag. Initial value: OFF. Tasks working on these features can enable them for their test orgs 

The three epics' tenant surfaces are behind plan switches, all OFF: production_qa (Deployments, Incidents…), a new agent_performance (outcome ledger), and intelligent_routing (task routing). Off = 403 and hidden; the operator passes; the org override turns each on. Quick gate and changed-area tests green; visual check done. PR #7678 merged by the lane (b5363e1); its Jaah Deploy was superseded by a newer push.