Add Gitea build, container tests and registry publication

Dockerfile

@@ -5,9 +5,16 @@ COPY agiledancers-be/pom.xml agiledancers-be/pom.xml
 COPY agiledancers-be/src agiledancers-be/src
 RUN mvn -B -ntp clean verify
 
-FROM eclipse-temurin:25-jre
+FROM eclipse-temurin:25-jre AS runtime
 WORKDIR /app
-COPY --from=build --chown=10001:10001 /workspace/agiledancers-be/target/quarkus-app/ ./
 USER 10001:10001
 EXPOSE 8080
 ENTRYPOINT ["java", "-jar", "/app/quarkus-run.jar"]
+
+# CI packages the exact output that already passed mvn clean verify.
+FROM runtime AS prebuilt
+COPY --chown=10001:10001 agiledancers-be/target/quarkus-app/ ./
+
+# Default standalone build still compiles and tests from source.
+FROM runtime AS standalone
+COPY --from=build --chown=10001:10001 /workspace/agiledancers-be/target/quarkus-app/ ./