fix: use model_dump() for Redis cache serialization - prevents 500 on cached equipment API calls

backend/app/routers/equipment.py

@@ -49,7 +49,7 @@ async def list_equipment(
     items = result.scalars().all()
 
     response = {
-        "items": [EquipmentItem.model_validate(item) for item in items],
+        "items": [EquipmentItem.model_validate(item).model_dump() for item in items],
         "total": total,
         "page": page,
         "page_size": page_size,
@@ -85,6 +85,6 @@ async def get_equipment(equipment_id: int, db: AsyncSession = Depends(get_db)) -
     item = result.scalar_one_or_none()
     if not item:
         raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="Equipment not found")
-    response = EquipmentDetail.model_validate(item)
+    response = EquipmentDetail.model_validate(item).model_dump()
     await cache.set(cache_key, response.model_dump(), ttl=3600)
     return response