feat: CNB exchange rates, multi-currency KPI stats, invoice PDF VAT in CZK

- ČNB exchange rate service with date-specific rates and caching
- Invoice/received invoice stats convert foreign currencies to CZK
- Dashboard revenue converts all currencies to CZK
- Invoice PDF: VAT recap table always in CZK with CNB rate footer
- Inline styles replaced with utility classes (step 4 cleanup)
- Spinner animation exempt from prefers-reduced-motion

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/routes/admin/invoices-pdf.ts

@@ -5,6 +5,8 @@ import { requirePermission } from "../../middleware/auth";
 import { localDateCzStr } from "../../utils/date";
 import { nasFinancialsManager } from "../../services/nas-financials-manager";
 import { htmlToPdf } from "../../utils/html-to-pdf";
+import { getRate } from "../../services/exchange-rates";
+import { localDateStr } from "../../utils/date";
 
 /* ── Helpers ─────────────────────────────────────────────────────── */
 
@@ -358,9 +360,12 @@ export default async function invoicesPdfRoutes(
         // QR generation failed — leave empty
       }
 
-      // VAT recapitulation (always in CZK)
+      // VAT recapitulation (always in CZK — Czech tax requirement)
       const isForeign = currency.toUpperCase() !== "CZK";
-      const cnbRate = 1.0; // Skip CNB rate conversion
+      const issueDateStr = invoice.issue_date
+        ? localDateStr(new Date(invoice.issue_date))
+        : undefined;
+      const cnbRate = isForeign ? await getRate(currency, issueDateStr) : 1.0;
       const vatRates = [21, 12, 0];
       const vatRecap: Array<{
         rate: number;
@@ -1007,6 +1012,17 @@ ${indentCSS}
       <tbody>
         ${vatRecapHtml}
       </tbody>
+      ${
+        isForeign
+          ? `<tfoot>
+        <tr>
+          <td colspan="4" style="font-size:0.7em; color:#666; padding-top:6px; text-align:left;">
+            Přepočet kurzem ČNB ke dni ${formatDate(invoice.issue_date)}: 1 ${escapeHtml(currency)} = ${cnbRate.toFixed(3).replace(".", ",")} CZK
+          </td>
+        </tr>
+      </tfoot>`
+          : ""
+      }
     </table>
   </div>