fix: use Harbor images with JDK for build

Dockerfile

@@ -1,8 +1,21 @@
-# Production image - JAR is pre-built locally
-FROM eclipse-temurin:17-jre-alpine
+# Multi-stage build using local Harbor images
+# Stage 1: Build JAR
+FROM harbor.cjjhc.top/library/openjdk:25-jdk-slim AS builder
 
 WORKDIR /app
-COPY target/*.jar app.jar
+
+# Install Maven
+RUN apt-get update && apt-get install -y maven && rm -rf /var/lib/apt/lists/*
+
+COPY pom.xml .
+COPY src ./src
+RUN mvn clean package -DskipTests
+
+# Stage 2: Production image
+FROM harbor.cjjhc.top/library/eclipse-temurin:25-jre-alpine
+
+WORKDIR /app
+COPY --from=builder /app/target/*.jar app.jar
 
 EXPOSE 8080