fix: 대체 아이템 삭제와 미사용 정리 기준 보정

backend/src/db.js

@@ -2027,37 +2027,57 @@ async function findUnusedCustomItems({ queryText = '' } = {}) {
   const whereClause = hasQuery ? 'WHERE c.label LIKE ? OR c.src LIKE ? OR u.email LIKE ? OR u.nickname LIKE ?' : ''
   const params = hasQuery ? [search, search, search, search] : []
 
-  const rows = await query(
-    `
-      SELECT
-        c.id,
-        c.owner_id,
-        c.src,
-        c.label,
-        c.replaced_by_item_id,
-        c.replaced_by_src,
-        c.replaced_by_label,
-        c.replaced_at,
-        c.created_at,
-        u.nickname,
-        u.email
-      FROM custom_items c
-      INNER JOIN users u ON u.id = c.owner_id
-      ${whereClause}
-      ORDER BY c.created_at DESC
-    `,
-    params
-  )
+  const [rows, topicItemRows, usageMeta] = await Promise.all([
+    query(
+      `
+        SELECT
+          c.id,
+          c.owner_id,
+          c.src,
+          c.label,
+          c.replaced_by_item_id,
+          c.replaced_by_src,
+          c.replaced_by_label,
+          c.replaced_at,
+          c.created_at,
+          u.nickname,
+          u.email
+        FROM custom_items c
+        INNER JOIN users u ON u.id = c.owner_id
+        ${whereClause}
+        ORDER BY c.created_at DESC
+      `,
+      params
+    ),
+    query(
+      `
+        SELECT ti.topic_id, tp.name AS topic_name, ti.src
+        FROM topic_items ti
+        LEFT JOIN topics tp ON tp.id = ti.topic_id
+      `
+    ),
+    getCustomItemUsageMeta(),
+  ])
+
+  const templateLinkedBySrc = new Map()
+  topicItemRows.forEach((row) => {
+    if (!row?.src) return
+    if (!templateLinkedBySrc.has(row.src)) templateLinkedBySrc.set(row.src, new Map())
+    templateLinkedBySrc.get(row.src).set(row.topic_id, {
+      id: row.topic_id,
+      name: row.topic_name || row.topic_id,
+    })
+  })
 
-  const { usageMap } = await getCustomItemUsageMeta()
   return rows
     .map((row) => ({
       ...mapCustomItemRow(row),
       ownerName: row.nickname || row.email,
       ownerEmail: row.email,
-      usageCount: usageMap.get(row.id) || 0,
+      usageCount: usageMeta.usageMap.get(row.id) || 0,
+      linkedTemplates: Array.from((templateLinkedBySrc.get(row.src) || new Map()).values()),
     }))
-    .filter((item) => item.usageCount === 0 || !!item.replacedAt)
+    .filter((item) => ((item.usageCount === 0 && item.linkedTemplates.length === 0) || !!item.replacedAt))
 }
 
 async function getFavoriteStatsForTierListIds(tierListIds, userId = '') {