training fix. add global settings

backend/models/ClassMapping.py

@@ -0,0 +1,25 @@
+from database.database import db
+
+class ClassMapping(db.Model):
+    """Class name mappings for training project details (3NF)"""
+    __tablename__ = 'class_mapping'
+    
+    id = db.Column(db.Integer, primary_key=True, autoincrement=True)
+    project_details_id = db.Column(db.Integer, db.ForeignKey('training_project_details.id', ondelete='CASCADE'), nullable=False)
+    label_studio_project_id = db.Column(db.Integer, db.ForeignKey('label_studio_project.project_id', ondelete='CASCADE'), nullable=False)
+    source_class = db.Column(db.String(255), nullable=False)
+    target_class = db.Column(db.String(255), nullable=False)
+    
+    # Unique constraint: each source class can only be mapped once per project details AND label studio project
+    __table_args__ = (
+        db.UniqueConstraint('project_details_id', 'label_studio_project_id', 'source_class', name='uq_class_mapping'),
+    )
+    
+    def to_dict(self):
+        return {
+            'id': self.id,
+            'project_details_id': self.project_details_id,
+            'label_studio_project_id': self.label_studio_project_id,
+            'source_class': self.source_class,
+            'target_class': self.target_class
+        }