Remove hardcoded container names for multi-instance deployment support

- Dashboard: auto-discovers containers from Docker network via socket
  proxy API instead of hardcoded 30-name list. Labels derived from
  docker compose service metadata.
- Email/Settings: mailhog host read from env.SMTP_HOST instead of
  hardcoded 'mailhog-changemaker' string
- Pangolin: grafana container derived from env.GRAFANA_URL hostname;
  newt container/service names from NEWT_CONTAINER_NAME/NEWT_COMPOSE_SERVICE
- SSRF blocklist: built dynamically from all service URL env vars
  instead of hardcoded hostname list
- New env vars: DOCKER_NETWORK_NAME, DOCKER_PROXY_URL,
  NEWT_CONTAINER_NAME, NEWT_COMPOSE_SERVICE

Bunker Admin

api/src/config/env.ts

@@ -205,6 +205,12 @@ const envSchema = z.object({
   MKDOCS_SITE_SERVER_URL: z.string().default('http://mkdocs-site-server-changemaker:80'),
   MKDOCS_SITE_SERVER_PORT: z.coerce.number().default(4004),
 
+  // Docker (container status dashboard + service management)
+  DOCKER_PROXY_URL: z.string().default('http://docker-socket-proxy:2375'),
+  DOCKER_NETWORK_NAME: z.string().default('changemaker-lite'),
+  NEWT_CONTAINER_NAME: z.string().default('newt-changemaker'),
+  NEWT_COMPOSE_SERVICE: z.string().default('newt'),
+
   // Monitoring Services (behind 'monitoring' profile)
   PROMETHEUS_URL: z.string().default('http://prometheus-changemaker:9090'),
   PROMETHEUS_PORT: z.coerce.number().default(9090),