Feature/blockchain sync service

[AugistineCreates]

Closes #197

Description

This PR introduces a service that periodically compares blockchain ownership/verification data with the application's database. It detects discrepancies and safely synchronizes the database without overwriting valid newer application state.

Changes Included

1. Periodic Sync Job: Configured vercel.json with a new cron job schedule and created the corresponding API route (app/api/cron/blockchain-sync/route.ts).
2. Blockchain Sync Repository: Added lib/blockchain-sync.repository.ts to fetch/update database snippets and log discrepancies.
3. Reconciliation Service: Added lib/blockchain-sync.service.ts with logic to detect mismatches, enforce safe reconciliation, and handle transient network failures with exponential backoff retries.
4. Database Schema: Included the example schema SQL script in scripts/add-blockchain-sync-log.sql for the blockchain_sync_log table.

Acceptance Criteria Met

• Blockchain data fetched periodically via scheduled background tasks.
• Discrepancies detected between on-chain and off-chain data.
• Safe reconciliation applied (database updated only when blockchain state is authoritative).
• No overwriting of newer application state.
• Traceability supported via logging mismatches and resolutions.
• Resilient to failures (retries applied for transient errors).

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