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/wwwroot/index.html

@@ -189,6 +189,7 @@
                     <a data-legal="privacy" href="/legal/privacy-en.html" target="_blank" data-i18n="legal.privacy">Privacy</a>
                     <a data-legal="cookies" href="/legal/cookies-en.html" target="_blank" data-i18n="legal.cookies">Cookies</a>
                 </div>
+                <span id="app-version" class="app-version"></span>
                 <a href="#top" class="back-to-top btn btn-dark btn-sm shadow" data-i18n="footer.top">Back to top</a>
             </div>
         </footer>