feat: Shared docker-compose for all Conduction apps

[rubenvdlinde]

Summary

• Adds a shared docker-compose.yml with all services previously scattered across openregister's compose files
• Includes GreenMail (lightweight test mail, --profile mail) and Open-Xchange (full groupware, --profile ox) for mail/PIM testing
• Adds seed scripts for mail (seed-mail.sh), PIM data (seed-pim.sh), and Open-Xchange (seed-ox.sh)
• Adds docs/development-environment.md with full documentation of all profiles, services, ports, and setup instructions
• Moves supporting docker files (postgres init, dolphin VLM, keycloak realm) to shared location

Profiles

Profile	Services	Purpose
(default)	db, nextcloud, exapp-n8n	Core dev environment
mail	greenmail	SMTP/IMAP test mail (ports 3025/3143/8085)
ox	open-xchange + ox-mariadb + ox-dovecot	Full groupware (port 8087)
ai	presidio, tgi-llm, dolphin-vlm, openanonymiser, exapp-openwebui	AI/LLM services
solr / search	solr, zookeeper	Search engine
elasticsearch	elasticsearch	Elasticsearch backend
commonground	keycloak, redis, livekit, minio + ExApps	Common Ground services
mariadb	db-mariadb, nextcloud-mariadb	MariaDB compatibility testing
openproject / integrations	openproject	Project management
xwiki / integrations	xwiki	Wiki platform
standalone	n8n, open-webui	Standalone versions (not ExApps)

Test plan

• docker compose -f .github/docker-compose.yml up -d starts core services
• --profile mail starts GreenMail, seed-mail.sh populates test accounts
• --profile ox starts Open-Xchange stack with MariaDB + Dovecot
• Nextcloud Mail app can connect to GreenMail (IMAP 3143 / SMTP 3025)
• seed-pim.sh creates contacts and calendar events in Nextcloud
• All app volume mounts resolve correctly from .github/ location