feat(infra): 添加 Docker Compose 配置和后端 Dockerfile (T004)

Dockerfile

@@ -0,0 +1,18 @@
+# Build stage: uses Maven + JDK 17 (Alpine) to compile and package the application.
+FROM maven:3.9-eclipse-temurin-17-alpine AS builder
+WORKDIR /app
+
+# Copy pom.xml first to leverage Docker layer caching for dependency downloads.
+COPY pom.xml .
+RUN mvn dependency:go-offline -q
+
+# Copy source and build the fat JAR, skipping tests.
+COPY src ./src
+RUN mvn clean package -DskipTests -q
+
+# Runtime stage: slim JRE-only image for a smaller production footprint.
+FROM eclipse-temurin:17-jre-alpine
+WORKDIR /app
+COPY --from=builder /app/target/*.jar app.jar
+EXPOSE 8080
+ENTRYPOINT ["java", "-jar", "app.jar"]