feat: complete variable management implementation and update documentation

- Update remaining Docker Compose templates with centralized variables
- Fix service tag isolation to deploy individual services only
- Update all README files with variable management architecture
- Document variable hierarchy in DEPLOYMENT_LEARNINGS.md
- Add comprehensive variable usage patterns to CLAUDE.md
- Standardize domain references using {{ subdomains.* }} pattern
- Replace hardcoded network names with {{ docker.network_name }}
- Update hairpinning configuration to use variables

🤖 Generated with [Claude Code](https://claude.ai/code)

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

roles/docker/templates/pingvin-compose.yml.j2

@@ -5,11 +5,11 @@ services:
     environment:
       - TRUST_PROXY=true
     extra_hosts:
-      - 'auth.thesatelliteoflove.com:172.20.0.5'
+      - '{{ subdomains.auth }}:{{ docker.hairpin_ip }}'
     labels:
       glance.name: Pingvin
       glance.icon: si:files
-      glance.url: http://netcup.porgy-porgy.ts.net:8945
+      glance.url: https://{{ subdomains.files }}
       glance.description: File sharing service
       glance.id: pingvin
     volumes:
@@ -21,4 +21,4 @@ volumes:
 networks:
   default:
     external: true
-    name: lava
+    name: {{ docker.network_name }}