docs(devops): update all documentation for DockerSpec compliance

- Replace all docker-compose.yml/docker-compose.monitoring.yml references with
  compose.yaml/compose.monitoring.yaml (modern Compose Spec naming)
- Replace all `docker-compose` CLI commands with `docker compose` (plugin syntax)
- Update Dockerfile stage descriptions: node:18-alpine → node:20.11-bookworm-slim,
  built-in node user → explicit nodeapp:1001 non-root user
- Update image version references: postgres:14-alpine → postgres:14.12-alpine3.19,
  redis:7-alpine → redis:7.2-alpine3.19
- Externalize postgres credentials: hardcoded values → POSTGRES_USER/PASSWORD/DB env vars
- Externalize Grafana admin password: hardcoded 'agentidp' → GF_ADMIN_PASSWORD env var
- Add Docker Compose Variables section to environment-variables.md (POSTGRES_*, GF_ADMIN_PASSWORD)
- Update local-development.md Step 3: cp .env.example .env, document POSTGRES_* purpose
- Update quick-start.md: cp .env.example .env, use awk/sed for JWT key injection
- Update 07-dev-setup.md: remove 'no .env.example' claim, reference cp .env.example
- Update docker-compose.yml key file description in 04-codebase-structure.md
- Update monitoring overlay launch commands across all docs (compose.yaml + compose.monitoring.yaml)
- Update volume names to kebab-case: postgres_data → postgres-data, redis_data → redis-data
- Fix compliance encryption-runbook: docker-compose restart agentidp → docker compose restart app

All docs now consistent with compose.yaml in repo root.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

docs/engineering/05-services.md

@@ -332,10 +332,10 @@ not exposed to the public internet.
 
 Start the monitoring overlay:
 ```bash
-docker compose -f docker-compose.yml -f docker-compose.monitoring.yml up
+docker compose -f compose.yaml -f compose.monitoring.yaml up
 ```
 - Prometheus: `http://localhost:9090`
-- Grafana: `http://localhost:3001` — default credentials: `admin` / `agentidp`
+- Grafana: `http://localhost:3001` — credentials: `admin` / `<GF_ADMIN_PASSWORD from .env>`
 
 Grafana is pre-provisioned with a Prometheus data source pointing to `http://prometheus:9090`
 and dashboard JSON files from `monitoring/grafana/dashboards/`. No manual configuration