fix(e2e): add /api/invoices/stats/summary mock before broad /api/invoices catch-all

PR #341 added a useEffect in the Invoices page that fetches
/api/invoices/stats/summary. The existing /api/invoices mock was too broad
and intercepted this URL, returning { data: [], total: 0 } instead of the
stats shape { revenueThisMonth, outstanding, refundsThisMonth, methodBreakdown }.
This caused a runtime crash when rendering paymentStats.revenueThisMonth.

The fix adds a specific mock for /api/invoices/stats/summary before the general
/api/invoices mock, so the stats endpoint returns the correct shape.

Fixes GRO-820.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

apps/e2e/tests/navigation.spec.ts

@@ -44,6 +44,17 @@ test.beforeEach(async ({ page }) => {
         json: { newClients: [], activeInPeriodCount: 0, churnRisk: [], churnRiskTotal: 0 },
       });
     }
+    // Specific route must come before /api/invoices to avoid intercepting stats/summary
+    if (url.includes("/api/invoices/stats/summary")) {
+      return route.fulfill({
+        json: {
+          revenueThisMonth: 0,
+          outstanding: 0,
+          refundsThisMonth: 0,
+          methodBreakdown: [],
+        },
+      });
+    }
     if (url.includes("/api/invoices")) {
       return route.fulfill({ json: { data: [], total: 0 } });
     }