feat(server): add POST /attachment/location mirroring product shelving

Co-Authored-By: Claude <noreply@anthropic.com>

app/services/attachment_service.py

@@ -198,3 +198,62 @@ def configure_attachment(db: Session, req: AttachmentConfigRequest) -> dict:
 
     db.commit()
     return get_attachment_status(db, zongpai_no)
+
+
+def _is_transit_location(location_code: str) -> bool:
+    return location_code.startswith("TRANS-")
+
+
+def _is_temp_storage_location(location_code: str) -> bool:
+    return location_code.startswith("B")
+
+
+def register_attachment_location(db: Session, req) -> FinishedGoodsAttachmentLocation:
+    zongpai_no = _validate_zongpai(req.zongpai_no)
+
+    # Category must exist
+    if not _category_name_map(db, [req.category_id]):
+        raise CategoryNotFoundError(req.category_id)
+
+    existing = (
+        db.query(FinishedGoodsAttachmentLocation)
+        .filter(
+            FinishedGoodsAttachmentLocation.zongpai_no == zongpai_no,
+            FinishedGoodsAttachmentLocation.category_id == req.category_id,
+        )
+        .first()
+    )
+    if existing:
+        if _is_transit_location(existing.location_code):
+            raise AlreadyOffShelfAttachmentError(
+                location_code=existing.location_code,
+                registered_at=existing.created_at.isoformat(),
+            )
+
+        target_is_transit = _is_transit_location(req.location_code)
+        target_is_temp = _is_temp_storage_location(req.location_code)
+        current_is_temp = _is_temp_storage_location(existing.location_code)
+
+        if target_is_transit or (not current_is_temp and target_is_temp):
+            previous_location = existing.location_code
+            existing.location_code = req.location_code
+            existing.created_at = datetime.now()
+            db.commit()
+            db.refresh(existing)
+            existing.previous_location = previous_location
+            return existing
+
+        raise DuplicateAttachmentLocationError(
+            location_code=existing.location_code,
+            registered_at=existing.created_at.isoformat(),
+        )
+
+    record = FinishedGoodsAttachmentLocation(
+        zongpai_no=zongpai_no,
+        category_id=req.category_id,
+        location_code=req.location_code,
+    )
+    db.add(record)
+    db.commit()
+    db.refresh(record)
+    return record