feat: add signed PostgreSQL release updates

oa-backend/build.gradle

@@ -5,7 +5,12 @@ plugins {
 }
 
 group = 'com.kaidi'
-version = '0.1.0'
+version = providers.gradleProperty('releaseVersion')
+        .orElse(System.getenv('ERP_RELEASE_VERSION') ?: '0.1.0')
+        .get()
+def productionBuild = providers.gradleProperty('productionBuild')
+        .map { it.toBoolean() }
+        .orElse(false)
 
 java {
     sourceCompatibility = JavaVersion.VERSION_17
@@ -23,10 +28,17 @@ dependencies {
     // Real-time collaboration (yjs CRDT relay) over WebSocket.
     implementation 'org.springframework.boot:spring-boot-starter-websocket'
 
-    // SQLite driver + Hibernate community dialects (SQLite dialect lives here).
-    // Version of hibernate-community-dialects is governed by Spring Boot's BOM.
-    runtimeOnly 'org.xerial:sqlite-jdbc:3.45.3.0'
-    implementation 'org.hibernate.orm:hibernate-community-dialects'
+    // Production database and versioned schema migrations.
+    implementation 'org.flywaydb:flyway-core:10.22.0'
+    runtimeOnly 'org.flywaydb:flyway-database-postgresql:10.22.0'
+    runtimeOnly 'org.postgresql:postgresql'
+
+    // SQLite remains available to source-tree development and tests, but is
+    // deliberately absent from PostgreSQL-only production release artifacts.
+    if (!productionBuild.get()) {
+        runtimeOnly 'org.xerial:sqlite-jdbc:3.45.3.0'
+        runtimeOnly 'org.hibernate.orm:hibernate-community-dialects'
+    }
 
     // jackson-databind arrives transitively via starter-web; declared for clarity.
     implementation 'com.fasterxml.jackson.core:jackson-databind'
@@ -41,3 +53,7 @@ dependencies {
 tasks.named('test') {
     useJUnitPlatform()
 }
+
+springBoot {
+    buildInfo()
+}