chore: remove the monitoring settings route and an unused query key

The root layout now reads the public monitoring switches while it
renders, so nothing calls GET /api/monitoring/settings any more (the
native client never did); the route and its unpublished entry in the
route coverage guard go. The Coach feedback card reads the AI quality
card's cell, which left queryKeys.adminCoachFeedback() without a reader.

src/__tests__/openapi-route-coverage-guard.test.ts

@@ -339,7 +339,6 @@ const UNPUBLISHED: Readonly<Record<string, Exemption>> = {
   "/api/internal/web-vitals": { kind: "internalOps", methods: ["POST"] },
   "/api/monitoring/csp-report": { kind: "internalOps", methods: ["POST"] },
   "/api/monitoring/glitchtip": { kind: "internalOps", methods: ["POST"] },
-  "/api/monitoring/settings": { kind: "internalOps", methods: ["GET"] },
   "/api/monitoring/umami-script": { kind: "internalOps", methods: ["GET"] },
   "/api/monitoring/umami/{path}": { kind: "internalOps", methods: ["POST"] },
   "/api/mcp/oauth/authorize": {