Add COD-in-transit summary and received tab to the dashboard

- GET /orders/summary: count and sum of cash-on-delivery for parcels not
  yet picked up (excludes received, refused, deleted/unknown TTNs, paid COD);
  shown as a card above the tabs.
- New «Полученные» tab: orders with NP received codes (9, 10, 11, 106) move
  there automatically, regardless of receipt; 106 is now a final status.

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

frontend/src/pages/DashboardPage.css

@@ -65,6 +65,39 @@
   justify-content: space-between;
 }
 
+.orders-summary {
+  display: flex;
+  gap: 16px;
+  flex-wrap: wrap;
+}
+
+.orders-summary-card {
+  display: flex;
+  flex-direction: column;
+  gap: 4px;
+  min-width: 220px;
+  padding: 14px 18px;
+  background: var(--color-surface);
+  border: 1px solid var(--color-border);
+  border-radius: 10px;
+}
+
+.orders-summary-label {
+  font-size: 13px;
+  color: var(--color-text-muted);
+}
+
+.orders-summary-value {
+  font-size: 22px;
+  font-weight: 700;
+  font-variant-numeric: tabular-nums;
+}
+
+.orders-summary-hint {
+  font-size: 12px;
+  color: var(--color-text-muted);
+}
+
 .orders-create-btn {
   border: none;
   background: var(--color-primary);