Add auto-incrementing version display to web UI footer

Exposes GET /version endpoint in the web container (reads APP_VERSION env var).
CI computes the version as 1.0.<git-commit-count> and passes it via --build-arg at build time.
Both index.html and cv-matcher/index.html show the version in the footer via a JS fetch.
docker-compose passes APP_VERSION through to the running container.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

docker-compose/docker-compose.yml

@@ -263,6 +263,7 @@ services:
       - ASPNETCORE_URLS=${ASPNETCORE_URLS:-http://+:8080}
       - APP_ENVIRONMENT_NAME=${APP_ENVIRONMENT_NAME:-myai.staging}
 
+      - APP_VERSION=${APP_VERSION:-unknown}
       - Site__Mode=${Site__Mode:-Normal}
     networks:
       - myai-network