feat: add location registration service

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

app/services/location_service.py

@@ -0,0 +1,34 @@
+from fastapi import HTTPException
+from sqlalchemy.orm import Session
+
+from app.models.finished_goods import FinishedGoodsLocation
+from app.schemas.location import LocationRequest
+
+
+def register_location(db: Session, req: LocationRequest) -> FinishedGoodsLocation:
+    existing = (
+        db.query(FinishedGoodsLocation)
+        .filter(FinishedGoodsLocation.zongpai_no == req.zongpai_no)
+        .first()
+    )
+    if existing:
+        raise HTTPException(
+            status_code=409,
+            detail={
+                "error_code": "DUPLICATE_LOCATION",
+                "message": "该总排号已存在货位记录",
+                "detail": {
+                    "existing_location": existing.location_code,
+                    "created_at": existing.created_at.isoformat(),
+                },
+            },
+        )
+
+    record = FinishedGoodsLocation(
+        zongpai_no=req.zongpai_no,
+        location_code=req.location_code,
+    )
+    db.add(record)
+    db.commit()
+    db.refresh(record)
+    return record