Google-Synced Fee Management App

I need a lightweight web application that keeps my fee records perfectly in-sync with an existing Google Sheet. The app must let me, as the sole Admin, log in through Google OAuth, view all incoming payments, mark them as received, and automatically push every change back to the sheet in real time.

Core workflow I expect
• Payment tracking – show current balances pulled from the sheet, allow quick status updates, and store a full change log.
• Automated reminders – send scheduled email notifications to any payer who still owes fees, using data in the sheet to determine amount and due date.
• Detailed reporting – generate monthly and ad-hoc summaries (total collected, outstanding, overdue) that I can download as CSV or view in the browser.

Tech flexibility is open, but please outline the stack you propose (e.g., Node.js with Express, Python Flask, or a low-overhead serverless option) and explain how you will handle the Google Sheets API, OAuth security, and email delivery.

Deliverables
1. Source code in a Git repo.
2. One-click deploy instructions (Docker or similar).
3. Short video or screenshots demonstrating payment update, reminder trigger, and report export.

The project is complete when I can log in with my Google account, update a fee, watch the sheet reflect the change instantly, and run a report that matches the data shown.