fix: “bulk retry failed rows” endpoint

[Aditya8369]

What changed

1. Schema: store retry inputs per row
   File: backend/models/BulkVerificationJob.js
   Change: added results[].originalInput (minimal record-like data: userid/email/walletaddress/action/signature/nonce/expiresat).
2. Persist original normalized inputs while processing
   File: backend/services/bulkVerificationService.js
   Change: each results.push(...) now includes originalInput (including for failures).
   Added: reconstructRetryRecords(failedRows) to transform stored originalInput back into the records shape expected by processJob().
3. Retry service
   File: backend/services/bulkVerificationService.js
   Added: retryJob(jobId, failedRows, adminId)
   creates a new BulkVerificationJob for the retry
   calls processJob(retryJobId, retryRecords, adminId, { dryRun:false }) in background
4. Controller + route
   File: backend/controllers/verificationController.js
   Added controller: retryBulkFailedRows
   validates jobId
   ensures original job exists and status === 'completed'
   selects job.results where status === 'failure'
   calls bulkVerificationService.retryJob(...)
   returns 202 with the new retry job id and counts

closes #444

[vercel]

@Aditya8369 is attempting to deploy a commit to the Nitya Gosain's projects Team on Vercel.

A member of the Team first needs to authorize it.