feat: Introduce SearchableCategoryField component and integrate it into admin panels for enhanced category selection

flutter/lib/features/admin/presentation/admin_inventory_panel.dart

@@ -4,6 +4,7 @@ import 'package:flutter_riverpod/flutter_riverpod.dart';
 
 import '../../../core/api/api_error_mapper.dart';
 import '../../../core/ui/category_then_product_picker.dart';
+import '../../../core/ui/searchable_category_field.dart';
 import '../../../core/ui/product_picker_field.dart';
 import '../data/admin_repository.dart';
 import '../domain/admin_category_node.dart';
@@ -38,6 +39,7 @@ class _AdminInventoryPanelState extends ConsumerState<AdminInventoryPanel> {
   List<AdminInventoryItem> _items = [];
   List<AdminProduct> _products = [];
   List<AdminCategoryNode> _categories = [];
+  List<CategorySelectOption> _categoryOptions = [];
   List<UserAdmin> _users = [];
 
   @override
@@ -67,6 +69,7 @@ class _AdminInventoryPanelState extends ConsumerState<AdminInventoryPanel> {
         _items = results[0] as List<AdminInventoryItem>;
         _products = results[1] as List<AdminProduct>;
         _categories = results[2] as List<AdminCategoryNode>;
+        _categoryOptions = _flattenCategoryOptions(_categories);
         _users = results[3] as List<UserAdmin>;
       });
     } catch (e) {
@@ -93,6 +96,20 @@ class _AdminInventoryPanelState extends ConsumerState<AdminInventoryPanel> {
     _InventorySort.quantityDesc => 'Mängd fallande',
   };
 
+  List<CategorySelectOption> _flattenCategoryOptions(
+    List<AdminCategoryNode> nodes, [
+    List<String> parents = const [],
+  ]) {
+    final result = <CategorySelectOption>[];
+    for (final node in nodes) {
+      final pathParts = [...parents, node.name];
+      final path = pathParts.join(' > ');
+      result.add((value: node.id.toString(), label: path));
+      result.addAll(_flattenCategoryOptions(node.children, pathParts));
+    }
+    return result;
+  }
+
   List<AdminInventoryItem> get _filtered {
     final q = _search.trim().toLowerCase();
     if (q.isEmpty) return _items;
@@ -803,6 +820,20 @@ class _InventoryFormDialogState extends State<_InventoryFormDialog> {
     super.dispose();
   }
 
+  void _applyCategorySelection(int id, String path) {
+    setState(() {
+      _categoryId = id;
+      _categoryPath = path;
+      _categorySearchController.text = path;
+      if (_productId != null) {
+        final current = _productById(_productId);
+        if (current?.categoryId != _categoryId) {
+          _productId = null;
+        }
+      }
+    });
+  }
+
   AdminProduct? _productById(int? id) {
     if (id == null) return null;
     for (final product in widget.products) {
@@ -829,16 +860,7 @@ class _InventoryFormDialogState extends State<_InventoryFormDialog> {
       preselectedCategoryId: _categoryId,
     );
     if (selected == null || !mounted) return;
-    setState(() {
-      _categoryId = selected.id;
-      _categoryPath = selected.path;
-      if (_productId != null) {
-        final current = _productById(_productId);
-        if (current?.categoryId != _categoryId) {
-          _productId = null;
-        }
-      }
-    });
+    _applyCategorySelection(selected.id, selected.path);
   }
 
   @override
@@ -888,19 +910,17 @@ class _InventoryFormDialogState extends State<_InventoryFormDialog> {
                   ),
                   const SizedBox(height: 12),
                 ],
-                GestureDetector(
-                  onTap: _pickCategory,
-                  child: InputDecorator(
-                    decoration: const InputDecoration(
-                      labelText: 'Kategori',
-                      border: OutlineInputBorder(),
-                    ),
-                    child: Text(
-                      _categoryPath == null || _categoryPath!.trim().isEmpty
-                          ? 'Tryck för att välja kategori'
-                          : _categoryPath!,
-                    ),
-                  ),
+                SearchableCategoryField(
+                  options: _categoryOptions,
+                  value: _categoryId?.toString(),
+                  label: 'Kategori (sökbar)',
+                  onChanged: (value) {
+                    if (value == null) return;
+                    final label = _categoryOptions
+                        .firstWhere((option) => option.value == value)
+                        .label;
+                    _applyCategorySelection(int.parse(value), label);
+                  },
                 ),
                 const SizedBox(height: 12),
                 Row(