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.

docs/API.md

@@ -1058,8 +1058,6 @@ scrape_configs:
     #   credentials: "<DASHBOARD_TOKEN>"
 ```
 
-A ready-to-run Prometheus + Grafana stack (four auto-provisioned dashboards; default home **CCAM — Overview**) lives in [`monitoring/`](../monitoring/README.md). **npm path (no Docker):** `npm run monitoring:install` then `npm run monitoring:up` (binaries are pulled via the monitoring package's `postinstall` — there is no official `grafana`/`prometheus` server package on npm). **Docker path:** `npm run monitoring:docker:up` or `npm run docker:full:up` (set `DASHBOARD_ALLOWED_HOSTS=host.docker.internal` on the dashboard when Prometheus runs in a container). Pre-built Prometheus console: `http://localhost:9090/consoles/index.html`.
-
 ---
 
 ### Pricing