Relates to CODAGT-713
Depends on #27285
This replaces the deployment-wide template allowlist UI with per-template Coder Agents controls. Each template's General Settings page exposes `agents_allowed` to organisation and template administrators through the existing template-update permission, whilst AI Settings > Templates gives deployment administrators a bulk management page. The bulk page requires both deployment-config and template-update permissions, reuses the same URL-backed server-side filter as `/templates`, tracks pending updates independently for each template, and surfaces failures through template-specific toasts. The copy refers to new workspace creation because disabling a template does not revoke an existing Coder Agent workspace.
This completes the frontend migration away from the experimental `/template-allowlist` API. #27515 removes the now-unused legacy storage, routes, SDK methods, generated types, and JSON utility. Later PRs add CLI flags and update the platform controls documentation. The stack is intended to merge as a unit.