fix(money): zero-decimal currency handling (D7)

Stripe sends zero-decimal currencies (JPY/KRW/VND/...) already in the
major unit; the unconditional /100 recorded a JPY dues charge 100x
understated in the ledger + receipt. minorToMajor is now currency-aware
(shared ZERO_DECIMAL_CURRENCIES/isZeroDecimalCurrency in
notifications-logic); formatMoney renders no fractional part for those.
Never fires for USD; closes silent ledger corruption for such tenants.
Tests added; suite 526+.

__tests__/notifications-logic.test.ts

@@ -85,6 +85,10 @@ describe('formatMoney', () => {
     expect(formatMoney(undefined, 'usd')).toBe('')
     expect(formatMoney(NaN, 'usd')).toBe('')
   })
+  it('renders zero-decimal currencies with no fractional part', () => {
+    expect(formatMoney(3000, 'jpy')).toBe('3000 JPY')
+    expect(formatMoney(50000, 'KRW')).toBe('50000 KRW')
+  })
 })
 
 describe('renderDuesEmail', () => {