Implement backend API and database services in Docker setup

- Added a new `api` service for the NestJS backend, including health checks and dependencies on PostgreSQL, Redis, and MinIO.
- Introduced PostgreSQL and Redis services with health checks and configurations for data persistence.
- Added MinIO for S3-compatible object storage and a one-shot service to initialize required buckets.
- Updated the Nginx configuration to proxy requests to the new backend API and MinIO storage.
- Enhanced the Dockerfile to support the new API environment variables and configurations.
- Updated the `package.json` and `package-lock.json` to include new dependencies for QR code generation and other utilities.

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/src/subscriptions/enums/flash-event.enum.ts

@@ -0,0 +1,7 @@
+export const flashEventType = [
+  'user_signed_up' as const,
+  'renewal_successful' as const,
+  'renewal_failed' as const,
+  'user_cancelled_subscription' as const,
+] as const;
+export type FlashEventType = (typeof flashEventType)[number];