feat: add Sentry, Cloudflare R2, and CloudFlare CDN integrations

Production quick wins for improved observability and scalability:

Sentry Error Tracking:
- Add sentry-sdk[fastapi] dependency
- Initialize Sentry in main.py with FastAPI/SQLAlchemy integrations
- Add Celery integration for background task error tracking
- Feature-flagged via SENTRY_DSN (disabled when empty)

Cloudflare R2 Storage:
- Add boto3 dependency for S3-compatible API
- Create storage_service.py with StorageBackend abstraction
- LocalStorageBackend for development (default)
- R2StorageBackend for production cloud storage
- Feature-flagged via STORAGE_BACKEND setting

CloudFlare CDN/Proxy:
- Create middleware/cloudflare.py for CF header handling
- Extract real client IP from CF-Connecting-IP
- Support CF-IPCountry for geo features
- Feature-flagged via CLOUDFLARE_ENABLED setting

Documentation:
- Add docs/deployment/cloudflare.md setup guide
- Update infrastructure.md with dev vs prod requirements
- Add enterprise upgrade checklist for scaling beyond 1000 users
- Update installation.md with new environment variables

All features are optional and disabled by default for development.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

docs/deployment/production.md

@@ -393,11 +393,70 @@ free -h
 
 ### Set Up Sentry (Error Tracking)
 
+Sentry provides real-time error tracking and performance monitoring.
+
+1. **Create a Sentry account** at [sentry.io](https://sentry.io) (free tier available)
+2. **Create a new project** (Python/FastAPI)
+3. **Add to `.env`**:
+   ```env
+   SENTRY_DSN=https://your-key@sentry.io/project-id
+   SENTRY_ENVIRONMENT=production
+   SENTRY_TRACES_SAMPLE_RATE=0.1
+   ```
+4. **Restart services**:
+   ```bash
+   sudo systemctl restart wizamart wizamart-celery
+   ```
+
+Sentry will now capture:
+- Unhandled exceptions
+- API errors with request context
+- Celery task failures
+- Performance traces (10% sample rate)
+
+---
+
+## Cloudflare R2 Storage
+
+For production, use Cloudflare R2 instead of local storage for scalability and CDN integration.
+
+### Setup
+
+1. **Create R2 bucket** in CloudFlare dashboard
+2. **Create API token** with Object Read/Write permissions
+3. **Add to `.env`**:
+   ```env
+   STORAGE_BACKEND=r2
+   R2_ACCOUNT_ID=your_account_id
+   R2_ACCESS_KEY_ID=your_access_key
+   R2_SECRET_ACCESS_KEY=your_secret_key
+   R2_BUCKET_NAME=wizamart-media
+   R2_PUBLIC_URL=https://media.yourdomain.com
+   ```
+
+See [CloudFlare Setup Guide](cloudflare.md) for detailed instructions.
+
+---
+
+## CloudFlare CDN & Proxy
+
+For production, proxy your domain through CloudFlare for:
+- Global CDN caching
+- DDoS protection
+- Free SSL certificates
+- WAF (Web Application Firewall)
+
+### Enable CloudFlare Headers
+
 Add to `.env`:
 ```env
-SENTRY_DSN=https://your-sentry-dsn
+CLOUDFLARE_ENABLED=true
 ```
 
+This enables proper handling of `CF-Connecting-IP` for real client IPs.
+
+See [CloudFlare Setup Guide](cloudflare.md) for complete configuration.
+
 ---
 
 ## Troubleshooting