[kelvin1john0901-blip]

#442 Standardize exception handling

• Add custom business-logic exception hierarchy (BusinessLogicException, PaymentExpiredException, InsufficientFundsException) in src/common/exceptions
• Replace service-layer throw new Error() with NestJS HTTP exceptions (BadRequestException/NotFoundException/ConflictException) so clients receive 400/404 instead of 500
• Implement global AllExceptionsFilter that logs all unhandled errors to Sentry and returns sanitized, stable error contracts; register it globally via APP_FILTER

#444 Encryption key rotation for Stellar wallet keys

• Add keyVersion column to blockchain_wallets (+ migration)
• Support ENCRYPTION_KEY_PREVIOUS fallback decryption and re-encryption in EncryptionService; new wallets are provisioned with current keyVersion
• Add re-encryptWallets() to BlockchainWalletService
• Add POST /api/v1/admin/encryption/rotate-key (SUPERADMIN) with audit log
• Document rotation procedure in RECOVERY_DRILL.md

#445 Settlement approval workflow for large settlements

• Implement SettlementsService.approveSettlement() / rejectSettlement() with audit log entry and merchant email notification on every decision
• Add POST /admin/settlements/:id/approve and /reject (SUPERADMIN only)
• Add paginated GET /admin/settlements list endpoint with Swagger docs

#446 Admin cron job management endpoints

• CronJobRegistry now tracks schedules; listJobs returns name, schedule, next run, and last run; getHistory returns paginated run logs (status, duration) persisted in CronJobLog; Swagger docs present

Closes #442
Closes #444
Closes #445
Closes #446