Fix Notification entity: add @Nationalized for NVARCHAR(MAX) column

- Hibernate validates body column expecting varchar(max) (CLOB)
- Migration creates it as NVARCHAR(MAX) for Unicode support
- Add @Nationalized annotation so Hibernate expects NVARCHAR(MAX)

Author: emmanuelknafo

backend/src/main/java/com/ontario/program/model/Notification.java

@@ -12,6 +12,8 @@
 import jakarta.persistence.Lob;
 import jakarta.persistence.ManyToOne;
 import jakarta.persistence.PrePersist;
+
+import org.hibernate.annotations.Nationalized;
 import jakarta.persistence.PreUpdate;
 import jakarta.persistence.Table;
 
@@ -41,6 +43,7 @@ public class Notification {
     private String subject;
 
     @Lob
+    @Nationalized
     @Column(name = "body", nullable = false)
     private String body;