Add Docker build, K8s manifests, and CI/CD deploy pipeline

- Dockerfile: multi-stage build with $BUILDPLATFORM for native Maven
  builds on ARM64 runners, amd64 runtime target. Passes REGISTRY_TOKEN
  build arg for cameleer3-common dependency resolution.
- K8s manifests: ClickHouse StatefulSet with init scripts ConfigMap,
  server Deployment + NodePort (30081)
- CI: docker job (QEMU + buildx cross-compile, registry cache,
  provenance=false, old image cleanup) + deploy job (kubectl)
- .dockerignore for build context optimization

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

Dockerfile

@@ -0,0 +1,26 @@
+FROM --platform=$BUILDPLATFORM maven:3.9-eclipse-temurin-17 AS build
+WORKDIR /build
+
+# Configure Gitea Maven Registry for cameleer3-common dependency
+ARG REGISTRY_TOKEN
+RUN mkdir -p ~/.m2 && \
+    echo '<settings><servers><server><id>gitea</id><username>cameleer</username><password>'${REGISTRY_TOKEN}'</password></server></servers></settings>' > ~/.m2/settings.xml
+
+COPY pom.xml .
+COPY cameleer3-server-core/pom.xml cameleer3-server-core/
+COPY cameleer3-server-app/pom.xml cameleer3-server-app/
+# Cache deps — only re-downloaded when POMs change
+RUN mvn dependency:go-offline -B || true
+COPY . .
+RUN mvn clean package -DskipTests -B
+
+FROM eclipse-temurin:17-jre
+WORKDIR /app
+COPY --from=build /build/cameleer3-server-app/target/cameleer3-server-app-*.jar /app/server.jar
+
+ENV SPRING_DATASOURCE_URL=jdbc:ch://clickhouse:8123/cameleer3
+ENV SPRING_DATASOURCE_USERNAME=cameleer
+ENV SPRING_DATASOURCE_PASSWORD=cameleer_dev
+
+EXPOSE 8081
+ENTRYPOINT exec java -jar /app/server.jar