feat: add HTTP healthcheck endpoint via quarkus-smallrye-health

- pom.xml: add quarkus-smallrye-health dependency.
  Exposes /q/health/live and /q/health/ready endpoints (liveness
  and readiness probes for Quarkus apps).
- Dockerfile: install curl-minimal in the microdnf layer so the
  container has a real HTTP client. quarkus-micro-image is based
  on UBI 9 minimal and doesn't ship with curl by default.
- compose.yaml: healthcheck now hits GET /q/health/live with
  curl -f instead of the previous kill -0 1 (which only proved
  the process was alive, not that the HTTP server was responding).

The next CI run will rebuild the native binary with the health
extension baked in; old images pulled from :latest will keep
working since this is additive.

pom.xml

@@ -68,6 +68,10 @@
             <groupId>io.quarkus</groupId>
             <artifactId>quarkus-smallrye-jwt-build</artifactId>
         </dependency>
+        <dependency>
+            <groupId>io.quarkus</groupId>
+            <artifactId>quarkus-smallrye-health</artifactId>
+        </dependency>
         <dependency>
             <groupId>io.quarkus</groupId>
             <artifactId>quarkus-elytron-security-common</artifactId>