Vale construir sua versão de ERPNext?

Build a small self-hosted bookkeeping and stock app for a one-person business. This is NOT an ERP replacement and should not pretend to be one.

Stack, no substitutions:
- Python 3.12, Django 5, SQLite, Django admin as the primary UI
- Plain Django templates for the few custom pages, no JS framework
- Run with `python manage.py runserver`, no Docker, no cloud, no accounts, no telemetry
- Secrets (SECRET_KEY only) read from .env via python-dotenv, ship .env.example

Data model:
- Account (code, name, type: asset/liability/equity/income/expense)
- JournalEntry (date, memo) with JournalLine (account, debit, credit); enforce that each entry balances to zero at save time and refuse to save if it does not
- Party (customer or supplier, single model with a flag)
- Item (sku, name, unit, sale price, purchase price, current qty)
- SalesInvoice and PurchaseInvoice, each with lines (item, qty, unit price); posting an invoice generates the matching JournalEntry and adjusts Item qty
- Payment (party, date, amount, direction) that also posts a JournalEntry

Behaviour:
- Seed a minimal chart of accounts on first migrate: Cash, Bank, Accounts Receivable, Accounts Payable, Sales, Purchases, Inventory, Owner Equity
- Invoices are draft or posted; posted invoices are immutable, corrections happen via a credit note that posts a reversing entry
- Inventory valuation is simple average cost, and say so plainly in the UI

Reports as read-only pages:
- Trial balance for a date range
- Profit and loss for a date range
- Balance sheet as of a date
- Stock on hand with average cost value
- Each report has a CSV download

Explicitly out of scope, do not build: manufacturing, payroll, multi-currency, tax engines, multi-user permissions, approval workflows, email sending.

Deliver README.md with setup in under five commands, a seed script that loads a few months of fake invoices and payments, and pytest tests covering: unbalanced entries are rejected, posting an invoice moves stock and hits the ledger, and the balance sheet actually balances.