feat(compliance): data classification fields and retention policies job [FASE-3.5]

backend/app/models/campaign.py

@@ -53,6 +53,7 @@ class Campaign(Base):
     target_platform = Column(String, nullable=True)
     tags = Column(JSONB, nullable=True, default=[])
     created_at = Column(DateTime(timezone=True), server_default=func.now())
+    data_classification = Column(String(20), nullable=False, server_default="internal")
 
     # Recurring scheduling fields
     is_recurring = Column(Boolean, default=False)