Should you build your own YNAB?

Build me a zero-based budgeting app to replace YNAB. Requirements:

- A local web app: Node + Express + better-sqlite3, server-rendered, binds to
  localhost only.
- Accounts (checking, credit card, cash) and categories in groups. Every dollar of
  inflow gets assigned; a To Be Budgeted header shows what is unassigned and goes
  red if I over-assign.
- Budget view: month grid of category · assigned · activity · available, with
  available balances rolling over month to month.
- Transactions: a fast keyboard entry form plus CSV import from bank exports, with
  payee-to-category memory so repeat payees auto-fill.
- Reconcile flow: enter the real bank balance, the app shows the difference and
  marks matched transactions cleared.
- Reports: spending by category per month and net worth over time, drawn with
  Chart.js.
- Nightly copy of budget.db to backups/budget-YYYY-MM-DD.db, keep 30.
- No accounts, no telemetry, and no bank credentials anywhere; CSV import is the
  only way money data enters.
- Out of scope: automatic bank sync, mobile apps, and shared budgets. A weekly CSV
  import is the habit that replaces sync.
- README: how to map my bank's CSV columns on first import.