feat: restore Runiczny Pancerz with Mana; NBP rates module with latest-rate fallback

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

tests/logic/nbp.test.ts

@@ -0,0 +1,31 @@
+import { describe, it, expect, vi } from 'vitest';
+import { fetchNbpRate } from '../../src/logic/nbp';
+
+const ok = (mid: number, effectiveDate: string) => ({ ok: true, json: async () => ({ rates: [{ mid, effectiveDate }] }) });
+const notFound = { ok: false, json: async () => ({}) };
+const now = new Date('2026-10-20');
+
+describe('fetchNbpRate', () => {
+  it('uses the June window for a past year', async () => {
+    const f = vi.fn().mockResolvedValue(ok(4.4, '2024-06-03'));
+    expect(await fetchNbpRate('EUR', 2024, now, f)).toEqual({ rate: 4.4, date: '2024-06-03' });
+    expect(f.mock.calls[0]![0]).toContain('/eur/2024-06-01/2024-06-14/');
+  });
+
+  it('uses the latest rate for a future year without a dated request', async () => {
+    const f = vi.fn().mockResolvedValue(ok(4.3, '2026-10-19'));
+    expect(await fetchNbpRate('eur', 2031, now, f)).toEqual({ rate: 4.3, date: '2026-10-19' });
+    expect(f).toHaveBeenCalledTimes(1);
+    expect(f.mock.calls[0]![0]).not.toMatch(/\d{4}-\d{2}-\d{2}\//);
+  });
+
+  it('falls back to the latest rate when the dated window has no table', async () => {
+    const f = vi.fn().mockResolvedValueOnce(notFound).mockResolvedValueOnce(ok(4.2, '2026-10-19'));
+    expect((await fetchNbpRate('eur', 2026, now, f))?.rate).toBe(4.2);
+  });
+
+  it('returns null when NBP is unreachable', async () => {
+    const f = vi.fn().mockRejectedValue(new Error('offline'));
+    expect(await fetchNbpRate('eur', 2024, now, f)).toBeNull();
+  });
+});