Fix review findings F1-F3 for Docker context, health check and version

F1: exclude generated internal/frontend/dist from the Docker build context.
F2: derive the health check host from MEALQUEST_HTTP_ADDR, mapping wildcard
hosts and localhost to 127.0.0.1 and keeping IPv6 brackets.
F3: compute the -dirty suffix ignoring the generated embed output, so a
rebuild of a clean checkout is not stamped dirty.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.dockerignore

@@ -10,6 +10,8 @@ design/
 node_modules
 web/node_modules
 web/dist
+# Generated embed output; the Go stage takes the PWA from the web stage.
+internal/frontend/dist/
 bin/
 *.db
 *.db-*