feat: add container registry configuration support

- Add CONTAINER_REGISTRY_URL and CONTAINER_TAG environment variables
- Configure for Gitea registry at http://gitea-http.taildb3494.ts.net/will/unitforge
- Add proper documentation and section formatting in .env.example
- Set default tag to 'latest'

.env.example

@@ -116,6 +116,15 @@ VALIDATION_CACHE_TTL=60
 # DOCKER_BUILDKIT=1
 # COMPOSE_DOCKER_CLI_BUILD=1
 
+# =============================================================================
+# CONTAINER REGISTRY CONFIGURATION
+# =============================================================================
+
+# Container registry URL for image publishing
+CONTAINER_REGISTRY_URL=http://gitea-http.taildb3494.ts.net/will/unitforge
+# Image tag for container builds
+CONTAINER_TAG=latest
+
 # =============================================================================
 # PATHS
 # =============================================================================