Fix Seafile upload response parsed as JSON; v2.0.15

Seafile seafhttp returns a plain file ID string, not JSON. Replaced
res.json() with res.text() — the return value was unused anyway.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

server/routes/nuggets-host-upload.js

@@ -132,7 +132,7 @@ async function uploadToSeafile(uploadLink, fileBuffer, filename, parentDir) {
     const body = await res.text()
     throw new Error(`Seafile upload failed (${res.status}): ${body}`)
   }
-  return res.json()
+  await res.text()
 }
 
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