修bug

src/components/PigBatchPenCard.vue

@@ -10,7 +10,7 @@
       <div class="info-item border-left">存栏: {{ pen.current_pig_count || 0 }}</div>
     </div>
     <div class="actions-section">
-      <el-button size="small" @click="emitAllocatePigs" :disabled="!isBatchActive">分配猪只</el-button>
+      <el-button size="small" @click="emitAllocatePigs" :disabled="!isBatchActive || batchUnassignedPigCount <= 0">分配猪只</el-button>
       <el-button size="small" type="danger" @click="emitRemove" :disabled="!isBatchActive || pen.current_pig_count > 0">移除</el-button>
     </div>
   </div>
@@ -29,6 +29,10 @@ export default {
     isBatchActive: {
       type: Boolean,
       default: true // 默认活跃，以防万一没有传递
+    },
+    batchUnassignedPigCount: {
+      type: Number,
+      default: 0
     }
   },
   emits: ['remove', 'allocate-pigs'],