docs(docker): Restructure deployment guide and add env var reference

Add Quick Run section with complete getting-started workflow including
admin user creation via --execute flag. Consolidate Docker Compose to
treat reverse proxy as essential with Traefik/Caddy/nginx examples.

Move detailed image building to development guide, keeping deployment
docs focused on using pre-built images.

Create environment variables reference with practical examples and
context. Clarify built-in TLS is for testing only; production should
use reverse proxies.

docs/reference/_meta.json

@@ -4,6 +4,11 @@
         "name": "config",
         "label": "Configuration"
     },
+    {
+        "type": "file",
+        "name": "environment-variables",
+        "label": "Environment Variables"
+    },
     {
         "type": "file",
         "name": "admin",