feat(miniprogram): add invoice thumb helper utilities.

Co-authored-by: Cursor <cursoragent@cursor.com>

miniprogram/scripts/test-bx-invoice-thumb.mjs

@@ -0,0 +1,53 @@
+import assert from 'node:assert/strict'
+import {
+  isImageFileType,
+  fileExtLabel,
+  formatInvoiceDateYmd,
+  buildAttachItemsFromInvoiceRows,
+  mergeInvoicePicksByDraftKeys
+} from '../utils/bxInvoiceThumb.js'
+
+assert.equal(isImageFileType('image/jpeg'), true)
+assert.equal(isImageFileType('application/pdf'), false)
+assert.equal(fileExtLabel('a.PDF'), 'PDF')
+assert.equal(formatInvoiceDateYmd('2026-09-16T12:00:00'), '2026-09-16')
+assert.equal(formatInvoiceDateYmd(''), '—')
+
+const rows = [
+  {
+    id: 'inv1',
+    amount: 100,
+    createTime: '2026-09-01T10:00:00',
+    attachments: [
+      { id: 'a1', fileName: 'x.jpg', fileType: 'image/jpeg' },
+      { id: 'a2', fileName: 'y.pdf', fileType: 'application/pdf' }
+    ]
+  }
+]
+const items = buildAttachItemsFromInvoiceRows(rows)
+assert.equal(items.length, 2)
+assert.equal(items[0].key, 'inv1:a1')
+assert.equal(items[1].fileName, 'y.pdf')
+
+const prev = [
+  {
+    key: 'inv9:a9',
+    invoiceId: 'inv9',
+    attachmentId: 'a9',
+    amount: 9,
+    createTime: '2026-08-01',
+    fileName: 'old.jpg',
+    fileType: 'image/jpeg',
+    previewUrl: 'http://old'
+  }
+]
+const merged = mergeInvoicePicksByDraftKeys(
+  ['inv9:a9', 'inv1:a1'],
+  items,
+  prev
+)
+assert.equal(merged.length, 2)
+assert.ok(merged.some((p) => p.key === 'inv9:a9' && p.previewUrl === 'http://old'))
+assert.ok(merged.some((p) => p.key === 'inv1:a1'))
+
+console.log('bxInvoiceThumb ok')