fix(security): complete security and delivery compliance remediation

backend/app/schemas/olt.py

@@ -0,0 +1,17 @@
+"""OLT response serialization."""
+from app.models.device import OLTDevice
+
+
+def serialize_olt(device: OLTDevice) -> dict:
+    """Return an OLT record without its device credential."""
+    return {
+        "id": device.id,
+        "ip_address": device.ip_address,
+        "username": device.username,
+        "slot_command": device.slot_command,
+        "region": device.region,
+        "location": device.location,
+        "description": device.description,
+        "created_at": device.created_at,
+        "updated_at": device.updated_at,
+    }