完璧に動作しています。

テスト	結果
確定取消 API	✅ is_confirmed: false, confirmed_at: null
USE トランザクション削除	✅ current_stock が 27.5→32 に復帰
引当再作成	✅ reserved_stock = 5.000 に復帰
追加した変更:

stock_service.py:81-93 — unconfirm_spreading(): USE削除→確定フラグリセット→引当再作成
fertilizer/views.py — unconfirm アクション（POST /api/fertilizer/plans/{id}/unconfirm/）
fertilizer/page.tsx — 一覧に「確定取消」ボタン（確定済み計画のみ表示）
FertilizerEditPage.tsx — 編集画面ヘッダーに「確定取消」ボタン + 在庫情報再取得

backend/apps/fertilizer/views.py

@@ -4,12 +4,19 @@ from django.http import HttpResponse
 from django.template.loader import render_to_string
 from rest_framework import viewsets, status
 from rest_framework.decorators import action
+from rest_framework.exceptions import ValidationError
 from rest_framework.permissions import IsAuthenticated
 from rest_framework.response import Response
 from rest_framework.views import APIView
 from weasyprint import HTML
 
 from apps.fields.models import Field
+from apps.materials.stock_service import (
+    confirm_spreading as confirm_spreading_service,
+    create_reserves_for_plan,
+    delete_reserves_for_plan,
+    unconfirm_spreading,
+)
 from apps.plans.models import Plan, Variety
 from .models import Fertilizer, FertilizationPlan, DistributionPlan
 from .serializers import (
@@ -33,7 +40,7 @@ class FertilizationPlanViewSet(viewsets.ModelViewSet):
 
     def get_queryset(self):
         qs = FertilizationPlan.objects.select_related('variety', 'variety__crop').prefetch_related(
-            'entries', 'entries__field', 'entries__fertilizer'
+            'entries', 'entries__field', 'entries__fertilizer', 'entries__fertilizer__material'
         )
         year = self.request.query_params.get('year')
         if year:
@@ -45,6 +52,20 @@ class FertilizationPlanViewSet(viewsets.ModelViewSet):
             return FertilizationPlanWriteSerializer
         return FertilizationPlanSerializer
 
+    def perform_create(self, serializer):
+        instance = serializer.save()
+        create_reserves_for_plan(instance)
+
+    def perform_update(self, serializer):
+        if serializer.instance.is_confirmed:
+            raise ValidationError({'detail': '確定済みの施肥計画は編集できません。'})
+        instance = serializer.save()
+        create_reserves_for_plan(instance)
+
+    def perform_destroy(self, instance):
+        delete_reserves_for_plan(instance)
+        instance.delete()
+
     @action(detail=True, methods=['get'])
     def pdf(self, request, pk=None):
         plan = self.get_object()
@@ -99,6 +120,67 @@ class FertilizationPlanViewSet(viewsets.ModelViewSet):
         response['Content-Disposition'] = f'attachment; filename="fertilization_{plan.year}_{plan.id}.pdf"'
         return response
 
+    @action(detail=True, methods=['post'], url_path='confirm_spreading')
+    def confirm_spreading(self, request, pk=None):
+        plan = self.get_object()
+
+        if plan.is_confirmed:
+            return Response(
+                {'detail': 'この計画は既に散布確定済みです。'},
+                status=status.HTTP_400_BAD_REQUEST,
+            )
+
+        entries_data = request.data.get('entries', [])
+        if not entries_data:
+            return Response(
+                {'detail': '実績データが空です。'},
+                status=status.HTTP_400_BAD_REQUEST,
+            )
+
+        actual_entries = []
+        for entry in entries_data:
+            field_id = entry.get('field_id')
+            fertilizer_id = entry.get('fertilizer_id')
+            if not field_id or not fertilizer_id:
+                return Response(
+                    {'detail': 'field_id と fertilizer_id が必要です。'},
+                    status=status.HTTP_400_BAD_REQUEST,
+                )
+            try:
+                actual_bags = Decimal(str(entry.get('actual_bags', 0)))
+            except InvalidOperation:
+                return Response(
+                    {'detail': 'actual_bags は数値で指定してください。'},
+                    status=status.HTTP_400_BAD_REQUEST,
+                )
+            actual_entries.append(
+                {
+                    'field_id': field_id,
+                    'fertilizer_id': fertilizer_id,
+                    'actual_bags': actual_bags,
+                }
+            )
+
+        confirm_spreading_service(plan, actual_entries)
+        plan.refresh_from_db()
+        serializer = self.get_serializer(plan)
+        return Response(serializer.data)
+
+    @action(detail=True, methods=['post'], url_path='unconfirm')
+    def unconfirm(self, request, pk=None):
+        plan = self.get_object()
+
+        if not plan.is_confirmed:
+            return Response(
+                {'detail': 'この計画はまだ確定されていません。'},
+                status=status.HTTP_400_BAD_REQUEST,
+            )
+
+        unconfirm_spreading(plan)
+        plan.refresh_from_db()
+        serializer = self.get_serializer(plan)
+        return Response(serializer.data)
+
 
 class CandidateFieldsView(APIView):
     """作付け計画から圃場候補を返す"""