feat(config-service): Centralized Configuration Management Service

[A6dulmalik]

Closes #356

Summary

Implements the centralized configuration management service at
microservices/config-service.

Changes

• Entities: Config, Environment, Secret, AuditLog, WebhookSubscription
• Endpoints:
  • GET/POST/PUT/DELETE /configurations – CRUD with caching and versioning
  • GET/POST/PUT/DELETE /environments – Environment management
    (dev/staging/production/test)
  • GET/POST/PUT/DELETE /secrets – AES-256-CBC encrypted secrets with rotation
  • GET/POST/PUT/DELETE /webhooks – HMAC-signed webhook delivery with retry
  • GET /audit-logs – Audit trail retrieval
• fix: registered AuditLogController in AuditModule so /audit-logs endpoints
  are reachable

Checklist

• Initialize NestJS project in microservices/config-service
• Set up Config, Environment, Secret entities
• Implement configuration endpoints
• Add environment-based config (dev/staging/prod)
• Create secret management (encrypted)
• Implement config caching
• Add real-time config updates via webhooks
• Create config versioning
• Implement config audit log
• Set up Docker configuration