Build a small inventory reorder-point calculator app (SQLite/Postgres + simple UI) — ~679 SKUs

We're a trailer- and motorcycle-parts company replacing an Excel reorder-point spreadsheet with a small, reliable internal app. The calculation logic already exists and is fully documented — we are NOT asking you to design a forecasting method. We need you to reproduce our existing spreadsheet formulas exactly in a clean database-backed tool with a simple interface. We have a written technical spec (database schema, the exact formulas, and an acceptance test) that we'll share with the selected freelancer. We also have a cleaned dataset of ~679 products ready to import. What we need built A database (SQLite is fine; Postgres acceptable) with four tables: products, suppliers, daily usage history, and calculation results. Schema is provided in our spec. A calculation module that reproduces three formulas from our spreadsheet exactly — a lead-time-window usage sum × a fixed safety factor (rounded), a year-over-year difference of actual weekly usage, and a final reorder point. The formulas are given verbatim in the spec. No averaging, smoothing, or alternative forecasting models — the whole point of our method is that it uses actual usage numbers, and proposals suggesting we "improve" the math will not be a fit. A simple UI (we're open to Retool, Appsmith, Budibase, ToolJet, or similar — your recommendation welcome) that lets a non-technical user: view/filter/sort the product table, click a button to run the recalculation, import a weekly/monthly usage CSV, and export results to CSV (full table and a specific column subset). A weekly "roll-forward": append the latest week's actual usage to history (never deleting prior history), then recalculate. A one-time data migration from our existing files into the new database. Critical requirement — please read Our product SKUs include values like 10-35, 1-00, and 99-999 that spreadsheet programs wrongly auto-convert into dates (e.g. 10-35 → Oct-35). This corruption is the entire reason we're rebuilding. The app's import process MUST treat SKUs as text and must never round-trip data through Excel/Google Sheets in a way that re-triggers this. Demonstrated understanding of this issue in your proposal will move you to the top of our list. Definition of done The app's calculated reorder points must match our existing spreadsheet's outputs cell-for-cell for a sample of SKUs we provide. We'll supply known input/output pairs as an acceptance test. The build is complete when those match and the import/recalculate/export buttons work end-to-end. Ideal skills Python (or your justified stack) for the calculation and import logic SQLite/Postgres An internal-tool/low-code UI platform (Retool, Appsmith, Budibase, ToolJet) OR a lightweight custom UI Clean data-migration / CSV handling experience Careful, detail-oriented — this is a correctness-critical financial/inventory tool, not a flashy front-end To apply, please tell us A similar internal tool you've built (link or description). Which UI platform you'd recommend for this and why. How you'd guarantee SKUs like 10-35 are never coerced into dates. Your estimated timeline and price. Confirm you're comfortable reproducing our exact formulas rather than substituting your own. What we'll provide A complete written technical spec (schema, exact formulas, acceptance test) A cleaned dataset of ~679 products with correct SKUs Sample input/output pairs for verification