fix(docker): remediate all DockerSpec violations for field trial

- Replace docker-compose.yml → compose.yaml (modern Compose Spec, no version header)
- Replace docker-compose.monitoring.yml → compose.monitoring.yaml
- Remove deprecated version: '3.x' headers from both compose files
- Add dedicated app-tier bridge network (no default bridge)
- Add restart: unless-stopped to all services
- Add deploy.resources.limits (memory + cpu) to all services
- Add healthcheck to app service (curl /health)
- Add healthchecks to prometheus and grafana in monitoring overlay
- Externalize postgres credentials to env vars (POSTGRES_USER/PASSWORD/DB)
- Externalize grafana admin password to GF_ADMIN_PASSWORD env var
- Make env_file optional (required: false) for CI/field-trial environments
- Update Dockerfile: node:18-alpine → node:20.11-bookworm-slim (pinned version)
- Add explicit non-root system user/group (nodejs:1001/nodeapp:1001)
- Add curl install to final stage for healthcheck probe
- Copy src/db/migrations from build stage (not host bind)
- Expand .dockerignore: tmp/, temp/, *.env.*, compose files, Dockerfiles
- Add .env.example to git (was ignored by .env.* rule — add !.env.example exception)
- Add POSTGRES_USER/PASSWORD/DB and GF_ADMIN_PASSWORD to .env.example

All compose files pass: docker compose config --quiet ✅

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

.dockerignore

@@ -1,7 +1,7 @@
-# Dependencies
+# Dependencies — never bake into image
 node_modules/
 
-# Compiled output (built inside Docker)
+# Compiled output — built inside Docker
 dist/
 
 # Test artifacts
@@ -10,7 +10,18 @@ tests/
 
 # Environment and secrets — never bake into image
 .env
+.env.*
 *.pem
+*.key
+*.cert
+
+# Docker files — not needed inside the image
+compose.yaml
+compose.*.yaml
+docker-compose.yml
+docker-compose*.yml
+Dockerfile*
+.dockerignore
 
 # Development workspace
 .cto-workspace/
@@ -21,11 +32,23 @@ next_steps.md
 # Git
 .git/
 .gitignore
+.gitattributes
 
 # Editor
 .vscode/
 .idea/
+*.swp
+*.swo
+
+# OS artifacts
+.DS_Store
+Thumbs.db
 
 # Logs
 *.log
 npm-debug.log*
+logs/
+
+# Temporary directories
+tmp/
+temp/