docs: add example.env and document all environment variables

- Create example.env with all 31 environment variables documented
- Update docker-compose.yml to use env_file directive
- Update doc/deployment.md with Quick Start and missing variables
- Add OXICLOUD_BASE_URL and WOPI configuration docs
- Update README.md Docker section with .env setup
- Remove duplicate port mapping (incorporates 4577e56)
- Fix server port default from 8085 to 8086

doc/wopi-integration.md

@@ -1055,7 +1055,6 @@ services:
       dockerfile: Dockerfile
     ports:
       - "8086:8086"
-      - "8085:8085"
     networks:
       - oxicloud
     depends_on: