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>

app/core/config.py

@@ -187,6 +187,28 @@ class Settings(BaseSettings):
     flower_url: str = "http://localhost:5555"
     flower_password: str = "changeme"  # CHANGE IN PRODUCTION!
 
+    # =============================================================================
+    # SENTRY ERROR TRACKING
+    # =============================================================================
+    sentry_dsn: str | None = None  # Set to enable Sentry
+    sentry_environment: str = "development"  # development, staging, production
+    sentry_traces_sample_rate: float = 0.1  # 10% of transactions for performance monitoring
+
+    # =============================================================================
+    # CLOUDFLARE R2 STORAGE
+    # =============================================================================
+    storage_backend: str = "local"  # "local" or "r2"
+    r2_account_id: str | None = None
+    r2_access_key_id: str | None = None
+    r2_secret_access_key: str | None = None
+    r2_bucket_name: str = "wizamart-media"
+    r2_public_url: str | None = None  # Custom domain for public access (e.g., https://media.yoursite.com)
+
+    # =============================================================================
+    # CLOUDFLARE CDN / PROXY
+    # =============================================================================
+    cloudflare_enabled: bool = False  # Set to True when using CloudFlare proxy
+
     model_config = {"env_file": ".env"}