chore(deployment): add deployment for backend

backend/.docker/Dockerfile

@@ -0,0 +1,32 @@
+# First stage: Build the application
+FROM gradle:jdk22 AS builder
+
+WORKDIR /app
+
+# Copy only Gradle wrapper and configuration files first (for caching efficiency)
+COPY gradlew build.gradle.kts settings.gradle.kts ./
+COPY gradle gradle
+
+# Give execute permissions to Gradle wrapper
+RUN chmod +x gradlew
+
+# Download dependencies first (improves caching)
+RUN ./gradlew dependencies
+
+# Copy the rest of the project files
+COPY src src
+
+# Build the application (skipping tests for faster build)
+RUN ./gradlew clean build -x test
+
+# Second stage: Run the application
+FROM openjdk:22-jdk-slim
+
+WORKDIR /app
+
+# Copy the built JAR from the first stage
+COPY --from=builder /app/build/libs/*.jar app.jar
+
+EXPOSE 8080
+
+ENTRYPOINT ["java", "-jar", "app.jar"]

backend/.dockerignore

@@ -0,0 +1,2 @@
+.gradle
+build

backend/src/main/resources/application.properties

@@ -1,4 +1,4 @@
-spring.datasource.url=jdbc:postgresql://localhost:5432/postgresdb
+spring.datasource.url=jdbc:postgresql://$DB_HOST}:5432/postgresdb
 spring.datasource.username=postgres_user
 spring.datasource.password=postgres_pass
 server.port=8080