Add collapsible sections to Ivanti Queue page

Group queue items into a hybrid layout: Inventory section (CARD/GRANITE/DECOM)
at top, then vendor-grouped sections for FP/Archer items sorted alphabetically.
Each section header is clickable to collapse/expand with chevron indicators.

- Extract grouping logic into reusable utility (queueGrouping.js)
- Add collapse state management (all sections expanded by default)
- Preserve cross-section multi-select, floating action bar, ticket badges
- Add 5 property-based tests covering grouping correctness, ordering,
  empty section omission, count accuracy, and selection independence

frontend/src/utils/queueGrouping.js

@@ -0,0 +1,63 @@
+/**
+ * Queue grouping utility — extracts the hybrid Inventory + vendor grouping logic
+ * from IvantiTodoQueuePage into a testable pure function.
+ *
+ * Spec: .kiro/specs/queue-collapsible-sections
+ * Requirements: 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7
+ */
+
+const INVENTORY_TYPES = new Set(['CARD', 'GRANITE', 'DECOM']);
+
+/**
+ * Groups visible queue items into the hybrid section layout.
+ *
+ * @param {Array} visibleItems - Queue items with status 'pending'
+ * @returns {Array<{key: string, label: string, type: string, items: Array}>}
+ *
+ * Rules:
+ * - Items with workflow_type CARD, GRANITE, or DECOM → Inventory section
+ * - Items with workflow_type FP or Archer → grouped by vendor field
+ * - Items with null/undefined/empty vendor → placed in "Unknown" vendor section
+ * - Inventory section appears first (if non-empty)
+ * - Vendor sections sorted alphabetically by label
+ * - Sections with zero items are omitted from output
+ */
+export function groupQueueItems(visibleItems) {
+  const inventoryItems = [];
+  const vendorMap = new Map();
+
+  for (const item of visibleItems) {
+    if (INVENTORY_TYPES.has(item.workflow_type)) {
+      inventoryItems.push(item);
+    } else {
+      const vendor = item.vendor?.trim() || 'Unknown';
+      if (!vendorMap.has(vendor)) vendorMap.set(vendor, []);
+      vendorMap.get(vendor).push(item);
+    }
+  }
+
+  const sections = [];
+
+  if (inventoryItems.length > 0) {
+    sections.push({
+      key: 'inventory',
+      label: 'Inventory',
+      type: 'inventory',
+      items: inventoryItems,
+    });
+  }
+
+  const sortedVendors = [...vendorMap.entries()]
+    .sort((a, b) => a[0].localeCompare(b[0]));
+
+  for (const [vendor, items] of sortedVendors) {
+    sections.push({
+      key: `vendor:${vendor}`,
+      label: vendor,
+      type: 'vendor',
+      items,
+    });
+  }
+
+  return sections;
+}