feat(items): support drag-and-drop reordering and contextual insert

Implement drag-and-drop sorting in the items grid
Add right-click context menu to insert new items before or after
Update backend to process insertion anchors during item creation

system-wordings.ts

@@ -707,6 +707,9 @@ export const systemWordingMessages = {
         createDefaultsMenu: 'New item options',
         createDefaultsTitle: 'Session defaults',
         clearCreateDefaults: 'Clear defaults',
+        itemActions: 'Item actions',
+        insertBeforeItem: 'Insert before',
+        insertAfterItem: 'Insert after',
         searchCategory: 'Search categories',
         searchUsage: 'Search usages',
         searchMethods: 'Search acquisition methods',
@@ -2042,6 +2045,9 @@ export const systemWordingMessages = {
         createDefaultsMenu: '新增物品选项',
         createDefaultsTitle: '当前会话默认值',
         clearCreateDefaults: '清除默认值',
+        itemActions: '物品操作',
+        insertBeforeItem: '在前面插入',
+        insertAfterItem: '在后面插入',
         searchCategory: '搜索分类',
         searchUsage: '搜索用途',
         searchMethods: '搜索入手方式',