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>

web/Dockerfile

@@ -13,6 +13,8 @@ FROM mcr.microsoft.com/dotnet/aspnet:10.0 AS final
 WORKDIR /app
 EXPOSE 8080
 ENV ASPNETCORE_URLS=http://0.0.0.0:8080
+ARG APP_VERSION=1.0.0
+ENV APP_VERSION=${APP_VERSION}
 
 COPY --from=build /app/publish .
 ENTRYPOINT ["dotnet", "web.dll"]