feat(analytics): add Dockerfile, CI workflow, and stable jar name for K8s deployment

- Pin jar output to analytics.jar (no version suffix) so Dockerfile COPY is stable
- Add Dockerfile based on apache/spark:3.5.4-scala2.13-java17-ubuntu
- Add versions.env (0.1.0) matching GitOps overlay image tag
- Add analytics-image.yml CI workflow following native-image.yml conventions

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

modules/analytics/build.gradle.kts

@@ -79,7 +79,11 @@ application {
 
 // Fat jar: includes runtimeClasspath (our code + pg driver + scala3-library)
 // but NOT compileOnly Spark jars.
+// archiveVersion is cleared so the output is always "analytics.jar" — stable
+// name required by the Dockerfile COPY instruction.
 tasks.jar {
+    archiveBaseName.set("analytics")
+    archiveVersion.set("")
     manifest {
         attributes["Main-Class"] = "de.nowchess.analytics.OpeningBookJob"
     }