op/datapack: add painting_variant JSON zip export button

데이터팩 수정 페이지에 "이미지.zip 출력" 버튼과 크기 입력(기본 4, 1~16)
을 추가. 누르면 GET /op/datapack/:key/images-zip?size=N 으로 음악 개수만큼
cover_NN.json (asset_id, width=size, height=size, title, author) 을 zip 으로
스트리밍해서 내려준다. 사용자가 맵 데이터팩의 data/musicquiz/painting_variant/
에 그대로 풀어 넣을 수 있다.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/server/routes/op.ts

@@ -1,4 +1,5 @@
 import { Router } from 'express'
+import archiver from 'archiver'
 import {
   createPack,
   deletePackKeys,
@@ -252,6 +253,48 @@ opRouter.get('/op/datapack/:packName/generate', requireAuth, async (req, res, ne
   }
 })
 
+// painting_variant JSON 들을 zip 으로 묶어 내려준다.
+// query.size 로 width/height (블록 단위, 기본 4, 1~16) 지정. 음악 개수만큼 cover_NN.json 생성.
+opRouter.get('/op/datapack/:packName/images-zip', requireAuth, async (req, res, next) => {
+  try {
+    const packKey = sanitizePackKey(pickFirstValue(req.params.packName))
+    const definition = await loadPackDefinition(packKey)
+    if (!definition) {
+      res.status(404).type('text/plain').send(t('errors.packNotFoundJson'))
+      return
+    }
+    const sizeRaw = Number(pickFirstValue(req.query.size))
+    const size = Number.isFinite(sizeRaw) && sizeRaw >= 1 && sizeRaw <= 16
+      ? Math.floor(sizeRaw)
+      : 4
+    const list = await loadPackList(packKey)
+    const total = list.music.length
+
+    res.setHeader('Content-Type', 'application/zip')
+    res.setHeader(
+      'Content-Disposition',
+      `attachment; filename="${packKey}-painting-variants.zip"`
+    )
+    const archive = archiver('zip', { zlib: { level: 9 } })
+    archive.on('error', (err) => next(err))
+    archive.pipe(res)
+    for (let i = 1; i <= total; i++) {
+      const nn = String(i).padStart(2, '0')
+      const json = {
+        asset_id: `musicquiz:cover_${nn}`,
+        width: size,
+        height: size,
+        title: { text: `Cover ${nn}` },
+        author: { text: 'music quiz' }
+      }
+      archive.append(JSON.stringify(json, null, 2) + '\n', { name: `cover_${nn}.json` })
+    }
+    await archive.finalize()
+  } catch (error) {
+    next(error)
+  }
+})
+
 opRouter.post('/op/dashboard/:packName', requireAuth, async (req, res, next) => {
   try {
     const packKey = sanitizePackKey(pickFirstValue(req.params.packName))