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/css/myai.css

@@ -607,6 +607,13 @@ img {
     flex-wrap: wrap
 }
 
+.app-version {
+    font-size: .7rem;
+    color: var(--muted);
+    opacity: .5;
+    font-family: monospace
+}
+
 .cookie-overlay {
     position: fixed;
     left: 0;