fix(aria): add BIGSERIAL PK to device_security_posture, fix JPA persist error

V4 migration drops the device_id primary key and adds an auto-generated
id BIGSERIAL as the PK. device_id becomes a unique nullable column.
Agents that don't send a numeric deviceId can now save posture reports.
Controller GET /{deviceId} now uses findByDeviceId instead of findById.

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

src/main/java/com/hiveops/aria/controller/DevicePostureController.java

@@ -66,7 +66,7 @@ public class DevicePostureController {
     @GetMapping("/{deviceId}")
     @PreAuthorize("hasAnyRole('MSP_ADMIN','BCOS_ADMIN')")
     public ResponseEntity<DeviceSecurityPosture> getPosture(@PathVariable Long deviceId) {
-        return postureRepository.findById(deviceId)
+        return postureRepository.findByDeviceId(deviceId)
                 .map(ResponseEntity::ok)
                 .orElse(ResponseEntity.notFound().build());
     }

src/main/java/com/hiveops/aria/entity/DeviceSecurityPosture.java

@@ -15,6 +15,10 @@ import java.time.Instant;
 public class DeviceSecurityPosture {
 
     @Id
+    @GeneratedValue(strategy = GenerationType.IDENTITY)
+    @Column(name = "id")
+    private Long id;
+
     @Column(name = "device_id")
     private Long deviceId;
 

src/main/java/com/hiveops/aria/repository/DeviceSecurityPostureRepository.java

@@ -13,6 +13,8 @@ public interface DeviceSecurityPostureRepository extends JpaRepository<DeviceSec
 
     Optional<DeviceSecurityPosture> findByDeviceAgentId(String deviceAgentId);
 
+    Optional<DeviceSecurityPosture> findByDeviceId(Long deviceId);
+
     Page<DeviceSecurityPosture> findAllByOrderByPostureScoreAsc(Pageable pageable);
 
     Page<DeviceSecurityPosture> findByPostureScoreLessThanOrderByPostureScoreAsc(

src/main/resources/db/migration/V4__add_posture_id_pk.sql

@@ -0,0 +1,13 @@
+-- device_security_posture used device_id BIGINT as its primary key,
+-- requiring callers to supply the numeric device ID. Agents only know
+-- their string deviceAgentId, so inserts without a deviceId failed.
+-- Add a proper auto-generated id column as the PK; make device_id a
+-- nullable unique column (FK concept, populated when known).
+
+ALTER TABLE device_security_posture DROP CONSTRAINT device_security_posture_pkey;
+
+ALTER TABLE device_security_posture
+    ADD COLUMN id BIGSERIAL PRIMARY KEY;
+
+ALTER TABLE device_security_posture
+    ADD CONSTRAINT uq_posture_device_id UNIQUE (device_id);