fix: remove spring-boot-starter-data-rest (security vulnerability)

Data REST was auto-exposing raw JPA repository endpoints (/appUsers,
/documents, /persons, /userGroups, etc.) that completely bypass the
@RequirePermission AOP checks — effectively making the entire database
readable and writable without authentication.

All API needs are covered by the custom controllers. The generated
api.ts is reverted to the stub until npm run generate:api is re-run
against the cleaned backend.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/pom.xml

@@ -38,10 +38,6 @@
 			<groupId>org.springframework.boot</groupId>
 			<artifactId>spring-boot-starter-data-jpa</artifactId>
 		</dependency>
-		<dependency>
-			<groupId>org.springframework.boot</groupId>
-			<artifactId>spring-boot-starter-data-rest</artifactId>
-		</dependency>
 		<dependency>
 			<groupId>org.springframework.boot</groupId>
 			<artifactId>spring-boot-starter-jdbc</artifactId>
@@ -79,11 +75,6 @@
 			<artifactId>spring-boot-starter-data-jpa-test</artifactId>
 			<scope>test</scope>
 		</dependency>
-		<dependency>
-			<groupId>org.springframework.boot</groupId>
-			<artifactId>spring-boot-starter-data-rest-test</artifactId>
-			<scope>test</scope>
-		</dependency>
 		<dependency>
 			<groupId>org.springframework.boot</groupId>
 			<artifactId>spring-boot-starter-jdbc-test</artifactId>