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- Deleted outdated documentation files (`CONTENT-INTEGRATION-COMPLETE.md`, `CURSOR-MCP-SETUP.md`, `FINAL-STATUS.md`, `FIXES-APPLIED.md`, `INDEEHHUB-INTEGRATION.md`,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.

BACKEND_INTEGRATION.md

@@ -12,7 +12,7 @@ Frontend (Vue 3 + Tailwind)
 Integration Layer
     ├── API Services (Axios)
     ├── Nostr Client (nostr-tools)
-    └── Authentication (Cognito + Nostr)
+    └── Authentication (Nostr NIP-98)
     ↓
 Backend Services
     ├── indeehub-api (NestJS + PostgreSQL)
@@ -24,7 +24,7 @@ Backend Services
 ### ✅ 1. API Service Layer
 **Files Created:**
 - `src/services/api.service.ts` - Base HTTP client with token management
-- `src/services/auth.service.ts` - Authentication (Cognito + Nostr)
+- `src/services/auth.service.ts` - Authentication (Nostr)
 - `src/services/content.service.ts` - Content/projects API
 - `src/services/subscription.service.ts` - Subscription management
 - `src/services/library.service.ts` - User library and rentals
@@ -47,9 +47,7 @@ Backend Services
 - `src/components/AuthModal.vue` - Glassmorphic auth UI
 
 **Features:**
-- **Cognito Authentication**: Email/password login and registration
-- **Nostr Authentication**: NIP-07 browser extension support
-- **Hybrid Mode**: Link Nostr to Cognito accounts
+- **Nostr Authentication**: NIP-07 extension, NIP-46 remote signer, nsec private key
 - Session validation and automatic refresh
 - Protected routes with navigation guards