The full Purchases.tsx page at /purchases (multi-week tables, date range picker,
disputes/allowances rows, 24-week comparison chart) was already ported but had
no sidebar nav entry. Adds it under Invoices → Purchases Chart and removes the
simplified single-week PurchasesCalendar placeholder that replaced it.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Backend endpoint /api/reports/purchases/weekly existed but had no frontend.
Adds PurchasesCalendar page under Invoices > Purchases Chart: 7-day columns,
one row per supplier, each cell lists invoice chips (number + total) linking
to the invoice detail. Daily totals row in footer, prev/next week navigation.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>