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/hoarder-compose.yml.j2

@@ -10,8 +10,8 @@ services:
     env_file:
       - .env
     extra_hosts:
-      - 'auth.thesatelliteoflove.com:172.20.0.5'
-      - bookmarks.thesatelliteoflove.com:172.20.0.5
+      - '{{ subdomains.auth }}:{{ docker.hairpin_ip }}'
+      - '{{ subdomains.bookmarks }}:{{ docker.hairpin_ip }}'
     environment:
       MEILI_ADDR: http://meilisearch:7700
       DATA_DIR: /data
@@ -19,7 +19,7 @@ services:
     labels:
       glance.name: Karakeep
       glance.icon: si:wikibooks
-      glance.url: https://bookmarks.thesatelliteoflove.com/
+      glance.url: https://{{ subdomains.bookmarks }}/
       glance.description: Bookmark manager
       glance.id: karakeep
   chrome:
@@ -53,4 +53,4 @@ volumes:
 networks:
   default:
     external: true
-    name: lava
+    name: {{ docker.network_name }}