Add admin page at /admin/appconfig with a DataTable showing all application configurations. Inline dropdowns allow editing log level, engine level, payload capture mode, and metrics toggle directly from the table. Changes push to agents via SSE immediately. Also adds a config bar on the AgentHealth page (/agents/:appId) for per-application config management with the same 4 settings. Backend: GET /api/v1/config list endpoint, findAll() on repository, sensible defaults for logForwardingLevel/engineLevel/payloadCaptureMode. Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>