Senior Python Backend Engineer for B2B Web App

I have an existing, production B2B web app and need a senior Python backend engineer to take it the last mile to a pilot. Not greenfield, not a rebuild. Stack: Python, Flask, SQLAlchemy, PostgreSQL on Supabase with row-level security, Alembic, an Anthropic LLM extraction pipeline, a Playwright/requests web crawler, and a React front end on Railway. Near-term work is data quality and reliability: fixing lead deduplication, hardening crawler telemetry, repairing municipal site adapters, and finishing a tenant-scoped dashboard. Backend and data depth is the priority; React is secondary. I am the product owner and set priorities. Engagement starts with a small paid trial task, then ongoing hourly. I own all assets and infrastructure; you work in environments I own and use your own dev keys. Please do not propose moving off this stack or rewriting it.