refactor: update environment configuration and documentation

- Modified `.env.example` to reflect new API URL structure and added CDN configuration for external storage.
- Updated `.gitignore` to include deployment secrets and certificate files, ensuring sensitive information is not committed.
- Revised `BACKEND_INTEGRATION.md` to clarify authentication methods, replacing Cognito references with Nostr NIP-98.
- Deleted outdated documentation files (`CONTENT-INTEGRATION-COMPLETE.md`, `CURSOR-MCP-SETUP.md`, `FINAL-STATUS.md`, `FIXES-APPLIED.md`, `INDEEHHUB-INTEGRATION.md`, `PROJECT-COMPLETE.md`, `PROJECT-SUMMARY.md`) to streamline project documentation.

These changes enhance the clarity of the environment setup and improve the overall documentation structure for better developer onboarding.

ARCHITECTURE.md

@@ -0,0 +1,21 @@
+# IndeeHub Architecture — Legacy vs Decentralized
+
+**Full comparison with summary of changes and pros/cons:** [docs/ARCHITECTURE.html](docs/ARCHITECTURE.html)
+
+Open the HTML file in a browser for the complete architecture document.
+
+## Quick Reference
+
+| Layer       | Legacy                          | Current                    |
+| :---------- | :------------------------------ | :------------------------- |
+| Auth        | Cognito                         | Nostr (NIP-07, 46, 98)     |
+| Payments    | Stripe                          | BTCPay (Lightning)         |
+| Storage     | AWS S3 / CloudFront             | MinIO                      |
+| Database    | PostgreSQL (RDS)                | PostgreSQL                 |
+| Queue       | —                               | Redis + BullMQ             |
+| Relay       | External                        | Self-hosted nostr-rs-relay |
+| Deployment  | AWS ECS                         | Docker / Portainer         |
+| Frontend    | React                           | Vue 3 + Vite               |
+| Backend     | NestJS                          | NestJS                     |
+| Encryption  | BuyDRM/KeyOS (Widevine/FairPlay) | AES-128 HLS                |
+| Transcoding | External API (ECS)              | FFmpeg + MinIO             |