fix: treat missing return records as empty results

src/pages/return-packing/return-packing.vue

@@ -2,7 +2,6 @@
 	<view v-if="user" class="page-shell portal-page work-page">
 		<PortalHeader title="退货合箱" :user="user" fallback-url="/pages/module/module?key=inbound" />
 		<scroll-view class="work-scroll" scroll-y><view class="portal-content work-content">
-			<view class="work-heading"><text class="work-title">退货合箱</text><text class="work-subtitle">仅可合并当前仓、同一客户、已完成签收的退货单库存</text></view>
 			<view v-if="!result" class="work-card"><text class="card-title">添加退货单</text><ScanTargetInput name="returnNo" v-model="searchCode" label="退货单号" placeholder="扫描或输入完整退货单号" :active="true" @submit="search" /><button class="primary" :disabled="!searchCode.trim() || busy" @tap="search(searchCode)">{{ busy ? '查询中…' : '查询可合箱库存' }}</button></view>
 
 			<view v-if="candidates !== null && !result" class="section-gap"><view v-if="!candidates.length" class="empty-box"><text class="empty-copy">没有匹配的已完成退货单或可用库存</text></view><view v-else class="task-list"><button v-for="item in candidates" :key="item.returnNo" class="task-card candidate-card" @tap="addOrder(item)"><view class="row-head"><view><text class="business-code">{{ item.returnNo }}</text><text class="meta-line">客户参考号：{{ item.customerReferenceNo || '—' }}</text></view><text class="select-link">添加 ›</text></view></button></view></view>
@@ -46,7 +45,7 @@
 		methods: {
 			startScanner() { this.stopScanner(); this._stopScanner = startScanBroadcast({ onScan: (value) => { if (!this.busy) { this.searchCode = value; this.search(value) } }, onError: (error) => this.setError(error, '扫码广播注册失败') }) },
 			stopScanner() { if (this._stopScanner) this._stopScanner(); this._stopScanner = null },
-			async search(raw) { const value = String(raw?.detail?.value ?? raw ?? this.searchCode).trim(); if (!value || this.busy) return; this.searchCode = value; await this.run(async () => { const preview = await findPackingOrders(value); this.candidates = preview.orders.filter((item) => !this.selectedOrders.some((selected) => selected.returnNo === item.returnNo)); if (!this.candidates.length) playErrorSound(); else playSuccessSound() }, '查询可合箱退货单失败') },
+			async search(raw) { const value = String(raw?.detail?.value ?? raw ?? this.searchCode).trim(); if (!value || this.busy) return; this.searchCode = value; await this.run(async () => { const preview = await findPackingOrders(value); this.candidates = preview.orders.filter((item) => !this.selectedOrders.some((selected) => selected.returnNo === item.returnNo)); if (this.candidates.length) playSuccessSound() }, '查询可合箱退货单失败') },
 			async addOrder(item) { if (this.busy || !item?.returnNo) return; await this.run(async () => { const preview = await findPackingOrders(item.returnNo); const exact = preview.orders.filter((order) => order.returnNo === item.returnNo); if (exact.length !== 1 || !preview.customerKey) throw new Error('请扫描完整退货单号后重试'); const customerKey = this.selectedOrders[0]?.customerKey; if (customerKey && customerKey !== preview.customerKey) throw new Error('不同客户的退货单不能合箱'); const selected = [...this.selectedOrders, { ...exact[0], customerKey: preview.customerKey }]; this.previews = { ...this.previews, [item.returnNo]: preview }; updateWarehouseWork('returnPacking', { selectedOrders: selected, searchCode: '', quantities: this.validQuantities(selected, this.previews) }); this.candidates = null; playSuccessSound() }, '添加退货单失败') },
 			removeOrder(returnNo) { const selected = this.selectedOrders.filter((item) => item.returnNo !== returnNo); const previews = { ...this.previews }; delete previews[returnNo]; this.previews = previews; updateWarehouseWork('returnPacking', { selectedOrders: selected, quantities: this.validQuantities(selected, previews) }) },
 			validQuantities(selected, previews) { const available = new Map(); for (const order of selected) for (const item of previews[order.returnNo]?.skus || []) available.set(item.skuCode, (available.get(item.skuCode) || 0) + Number(item.availableQuantity || 0)); return Object.fromEntries([...available].map(([sku, maximum]) => [sku, Math.min(maximum, this.quantity(sku))])) },