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

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

apps/backend/scripts/migration/migrate-wrapper.sh

@@ -0,0 +1,13 @@
+#!/bin/bash
+# Migration wrapper script - loads .env before running tsx
+
+cd "$(dirname "$0")"
+
+# Load .env file
+if [ -f .env ]; then
+  export $(grep -v '^#' .env | xargs)
+  echo "✓ .env loaded"
+fi
+
+# Run the migration script
+tsx migrate.ts "$@"