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/07-dev-setup.md

@@ -44,18 +44,24 @@ development dependencies (TypeScript, Jest, ts-jest, eslint).
 
 ## 8.3 Environment Variables Setup
 
-The server requires a `.env` file at the project root. There is no `.env.example`
-file — create it from scratch using the template below.
+The server requires a `.env` file at the project root. Copy the template:
 
 ```bash
-touch .env
+cp .env.example .env
 ```
 
-Add the following content to `.env`. Every variable is documented below.
+The template includes all required variables with sensible local defaults. Edit `.env` to set your values. Key variables are documented below.
 
 ```bash
 # ─────────────────────────────────────────────────────────────
-# PostgreSQL connection
+# PostgreSQL — individual credentials for compose.yaml
+# ─────────────────────────────────────────────────────────────
+POSTGRES_USER=sentryagent
+POSTGRES_PASSWORD=sentryagent
+POSTGRES_DB=sentryagent_idp
+
+# ─────────────────────────────────────────────────────────────
+# PostgreSQL connection (application reads this directly)
 # ─────────────────────────────────────────────────────────────
 DATABASE_URL=postgresql://sentryagent:sentryagent@localhost:5432/sentryagent_idp