feat(backend): update collections, config and migration tools

Update Payload CMS configuration, collections (Audit, Posts), and add migration scripts/reports.

apps/backend/scripts/migration/test-env.ts

@@ -0,0 +1,15 @@
+#!/usr/bin/env tsx
+import { config as dotenvConfig } from 'dotenv'
+import { resolve, dirname } from 'path'
+import { fileURLToPath } from 'url'
+
+const __filename = fileURLToPath(import.meta.url)
+const __dirname = dirname(__filename)
+const envPath = resolve(__dirname, '../../.env')
+
+console.log('Loading .env from:', envPath)
+const result = dotenvConfig({ path: envPath })
+
+console.log('dotenv result:', result.error ? result.error.message : 'success')
+console.log('PAYLOAD_SECRET:', process.env.PAYLOAD_SECRET ? 'SET' : 'NOT SET')
+console.log('DATABASE_URI:', process.env.DATABASE_URI ? 'SET' : 'NOT SET')