Add X-Real-IP, X-Forwarded-Proto, X-Forwarded-Host, and X-Forwarded-Port headers to all proxy hosts for proper client IP detection, HTTPS enforcement, and logging.
- New feature flag: enable_standard_headers (default: true for new hosts, false for existing)
- UI: Checkbox in proxy host form and bulk apply modal for easy migration
- Security: Always configure trusted_proxies when headers enabled
- Backward compatible: Existing hosts preserve legacy behavior until explicitly enabled
BREAKING CHANGE: New proxy hosts will have standard headers enabled by default. Existing hosts maintain legacy behavior. Users can opt-in via UI.
Backend: 98.7% coverage, 8 new tests
Frontend: 87.7% coverage, full TypeScript support
Docs: Comprehensive migration guide and troubleshooting
Closes #<issue-number> (FileFlows WebSocket fix)