Round 4 improvements: automated config, relative paths, simplified deployment

- Automate Traefik email substitution in deploy script
- Auto-generate Authelia admin password (saved to ADMIN_PASSWORD.txt)
- Standardize all volume paths to use relative paths (./service/config)
- Switch Traefik to HTTP challenge by default (DNS challenge optional)
- Update documentation with improved setup instructions
- Enhance troubleshooting guide
- Update AGENT_INSTRUCTIONS with new conventions
- Simplify .env.example with clearer guidance

These changes reduce manual configuration steps and improve deployment reliability.

docker-compose/productivity.yml

@@ -188,7 +188,7 @@ services:
       - homelab-network
       - traefik-network
     volumes:
-      - /opt/stacks/dokuwiki/config:/config
+      - ./$(basename $file .yml)/config:/config
     environment:
       - PUID=${PUID:-1000}
       - PGID=${PGID:-1000}
@@ -214,7 +214,7 @@ services:
       - traefik-network
       - bookstack-network
     volumes:
-      - /opt/stacks/bookstack/config:/config
+      - ./$(basename $file .yml)/config:/config
     environment:
       - PUID=${PUID:-1000}
       - PGID=${PGID:-1000}