chore: remove unused desktop app, cloud deployment infra, and monitoring stack

Deletes desktop/ (Electron wrapper), deployments/ (Helm/Kustomize/
Terraform/CI for cloud deploy), and monitoring/ (Prometheus + Grafana
stack) along with DESKTOP.md, DEPLOYMENT.md, docker-compose.full.yml,
their npm scripts, and every dangling reference across README,
ARCHITECTURE, INSTALL, SETUP, docs/, and the repeated per-file
MODULE_GUIDE "Observability" boilerplate comment. The GET /api/metrics
endpoint itself is untouched — it's the dashboard's own route, not
part of the removed monitoring stack.

mcp/build/transports/repl.js

@@ -20,11 +20,6 @@
  * how to reach a peer dashboard; the global data scope (`dataScope.ts`) narrows every
  * scoped GET via `?sources=`. Health checks and import history surface in Settings.
  *
- * ## Observability
- * Prometheus scrapes `GET /api/metrics` (see `monitoring/`). Grafana ships four
- * provisioned boards (overview, sessions, tools, alerts). Native npm scripts and
- * Docker Compose profiles are documented in `monitoring/README.md`.
- *
  * ## Internal dependencies
  * - `../config/app-config.js`
  * - `../clients/dashboard-api-client.js`