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>

main.py

@@ -21,16 +21,41 @@ import logging
 from datetime import UTC, datetime
 from pathlib import Path
 
+import sentry_sdk
 from fastapi import Depends, FastAPI, HTTPException, Request, Response
 from fastapi.middleware.cors import CORSMiddleware
 from fastapi.responses import FileResponse, HTMLResponse, RedirectResponse
 from fastapi.staticfiles import StaticFiles
 from fastapi.templating import Jinja2Templates
+from sentry_sdk.integrations.fastapi import FastApiIntegration
+from sentry_sdk.integrations.sqlalchemy import SqlalchemyIntegration
 from sqlalchemy import text
 from sqlalchemy.orm import Session
 
 from app.api.main import api_router
 from app.core.config import settings
+
+# =============================================================================
+# SENTRY INITIALIZATION
+# =============================================================================
+# Initialize Sentry for error tracking (only if DSN is configured)
+if settings.sentry_dsn:
+    sentry_sdk.init(
+        dsn=settings.sentry_dsn,
+        environment=settings.sentry_environment,
+        traces_sample_rate=settings.sentry_traces_sample_rate,
+        integrations=[
+            FastApiIntegration(transaction_style="endpoint"),
+            SqlalchemyIntegration(),
+        ],
+        # Send PII data (emails, usernames) - set to False if privacy is critical
+        send_default_pii=True,
+        # Release version for tracking deployments
+        release=f"wizamart@{settings.version}",
+    )
+    logging.getLogger(__name__).info(
+        f"Sentry initialized for environment: {settings.sentry_environment}"
+    )
 from app.core.database import get_db
 from app.core.lifespan import lifespan
 from app.exceptions import ServiceUnavailableException