build(deploy): 添加多阶段 Dockerfile 以统一构建前后端

引入一个新的多阶段 `Dockerfile.build`，用于将 Flutter 前端和 Spring Boot 后端的构建过程整合到单个 Docker 镜像中。

- 第一阶段使用 Flutter 镜像构建 Web 静态资源。
- 第二阶段使用 Maven 镜像编译 Java 后端应用。
- 最终阶段将前两阶段的产物（Web 资源和 JAR 包）复制到一个精简的 JRE 基础镜像中，以创建最终的运行时镜像。

此变更简化了部署流程，并显著减小了最终生产镜像的体积。`docker-compose.yml` 已同步更新以使用此新的构建文件。

deploy/open/Dockerfile.build

@@ -0,0 +1,53 @@
+# Stage 1: Build the Flutter web client
+FROM cirrusci/flutter:3.22.2 as flutter_builder
+WORKDIR /app
+
+# Copy Flutter project files
+COPY AINoval/pubspec.yaml AINoval/pubspec.lock ./AINoval/
+RUN cd AINoval && flutter pub get
+
+# Copy the rest of the Flutter project source code
+COPY AINoval/ ./AINoval/
+
+# Build the Flutter web application
+RUN cd AINoval && flutter build web --release --web-renderer canvaskit
+
+# Stage 2: Build the Java Spring Boot server
+FROM maven:3.9-eclipse-temurin-21 as java_builder
+WORKDIR /app
+
+# Copy only the pom.xml to leverage Docker cache for dependencies
+COPY AINovalServer/pom.xml ./AINovalServer/
+RUN mvn -f AINovalServer/pom.xml dependency:go-offline
+
+# Copy the rest of the server source code
+COPY AINovalServer/ ./AINovalServer/
+
+# Build the application, skipping tests to speed up the process
+RUN mvn -f AINovalServer/pom.xml clean package -DskipTests
+
+# Stage 3: Create the final runtime image
+FROM eclipse-temurin:21-jre
+
+ENV TZ=Asia/Shanghai \
+    LANG=C.UTF-8 \
+    LC_ALL=C.UTF-8 \
+    SPRING_PROFILES_ACTIVE=prod \
+    JVM_XMS=512m \
+    JVM_XMX=512m
+
+# Fix JDK 21 reflective access for BigDecimal in Spring Data Mongo
+ENV JAVA_TOOL_OPTIONS="--add-opens=java.base/java.math=ALL-UNNAMED --add-opens=java.base/java.lang=ALL-UNNAMED --add-opens=java.base/java.time=ALL-UNNAMED --add-opens=java.base/java.util=ALL-UNNAMED --add-opens=java.base/java.util.concurrent=ALL-UNNAMED"
+
+WORKDIR /app
+
+# Copy the server jar from the java_builder stage and rename it
+COPY --from=java_builder /app/AINovalServer/target/ai-novel-server-0.0.1-SNAPSHOT.jar /app/ainoval-server.jar
+
+# Copy the built web assets from the flutter_builder stage
+COPY --from=flutter_builder /app/AINoval/build/web/ /app/web/
+
+EXPOSE 18080
+
+# Serve the prebuilt web from filesystem via Spring static locations
+CMD sh -c "java -Xms${JVM_XMS} -Xmx${JVM_XMX} -Dfile.encoding=UTF-8 -Dspring.web.resources.static-locations=file:/app/web/ -jar /app/ainoval-server.jar"

deploy/open/docker-compose.yml

@@ -19,7 +19,7 @@ services:
     image: ainoval/ainoval-server:latest
     build:
       context: ..
-      dockerfile: open/Dockerfile
+      dockerfile: open/Dockerfile.build
     container_name: ainoval-server
     env_file:
       - ./production.env