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

src/common/config.rs

@@ -439,7 +439,7 @@ impl Default for AppConfig {
         Self {
             storage_path: PathBuf::from("./storage"),
             static_path: PathBuf::from("./static"),
-            server_port: 8085,
+            server_port: 8086,
             server_host: "127.0.0.1".to_string(),
             cache: CacheConfig::default(),
             timeouts: TimeoutConfig::default(),