feat(admin): 分组能力按类型收口（应用可分组，海报/图文平铺）

- 只有应用类分区显示分组管理与卡片预览分组；海报/图文保持平铺
- 后端 create_group 拒绝非应用分区；海报/图文读取时把历史分组条目一并平铺
- 侧栏不再显示非应用分组与空分组
- 类型 应用 ↔ 海报 切换时分组入口和侧栏子项随之出现/消失
- 测试 59 passed

stash-web/src/components/admin/AdminPage.tsx

@@ -539,7 +539,7 @@ function SidebarForm({
               </div>
             ))}
 
-            {(
+            {category.kind === 'apps' && (
               <div className="admin-nav-group-row">
                 <NewGroupRow sectionId={category.id} onReload={onReload} />
               </div>
@@ -762,8 +762,12 @@ function CategoryManager({
             onReload={onReload}
             onDelete={onDelete}
           />
-          <BlockSelect section={category} onReload={onReload} />
-          <GroupManager section={category} onReload={onReload} />
+          {category.kind === 'apps' && (
+            <>
+              <BlockSelect section={category} onReload={onReload} />
+              <GroupManager section={category} onReload={onReload} />
+            </>
+          )}
         </div>
       ))}
 
@@ -1271,7 +1275,7 @@ function EntryDialog({
 
   const section =
     categories.find((category) => category.id === sectionId) ?? categories[0]
-  const groups = section?.groups ?? []
+  const groups = section?.kind === 'apps' ? (section.groups ?? []) : []
 
   // 打开时重置：新建用当前选择，编辑先拉完整条目
   useEffect(() => {
@@ -1281,10 +1285,10 @@ function EntryDialog({
     const startSection =
       defaultLocation?.sectionId ?? categories[0]?.id ?? ''
     setSectionId(startSection)
+    const startCategory = categories.find((category) => category.id === startSection)
     setGroupId(
       defaultLocation?.groupId ??
-        categories.find((category) => category.id === startSection)?.groups?.[0]?.id ??
-        '',
+        (startCategory?.kind === 'apps' ? (startCategory.groups?.[0]?.id ?? '') : ''),
     )
 
     if (entryKey === null) {
@@ -1322,16 +1326,23 @@ function EntryDialog({
     // eslint-disable-next-line react-hooks/exhaustive-deps
   }, [open, entryKey])
 
-  // 分区切换后保证分组仍然合法（空字符串 = 直属分区）
+  // 只有应用类分区有分组；其余类型始终是直属分区
   useEffect(() => {
-    if (section === undefined) return
+    if (section?.kind !== 'apps') {
+      if (groupId !== '') setGroupId('')
+      return
+    }
     if (groupId !== '' && !groups.some((group) => group.id === groupId)) {
       setGroupId(groups[0]?.id ?? '')
     }
   }, [section, groups, groupId])
 
   const nodeKey =
-    section === undefined ? '' : groupId !== '' ? groupId : section.id
+    section === undefined
+      ? ''
+      : section.kind === 'apps' && groupId !== ''
+        ? groupId
+        : section.id
 
   const update = (patch: Partial<EntryForm>) =>
     setForm((previous) => ({ ...previous, ...patch }))
@@ -1428,7 +1439,7 @@ function EntryDialog({
                 onChange={setSectionId}
               />
             </div>
-            {section !== undefined && (
+            {section?.kind === 'apps' && (
               <div style={{ width: 240 }}>
                 <Select
                   options={[

stash-web/src/components/sidebar/CategoryNav.tsx

@@ -38,9 +38,11 @@ export function CategoryNav({
   const items: MenuItem[] = [
     { key: HOME_KEY, label: '首页' },
     ...categories.map((category) => {
-      // 分组已由 App 按 /admin 的侧栏设置过滤、排序（含 show_in_sidebar 覆盖）；
-      // 应用 / 海报 / 图文都支持分组
-      const groups = category.groups
+      // 只有应用类有分组；空分组不出现在侧栏（后台仍保留）
+      const groups =
+        category.kind === 'apps'
+          ? category.groups.filter((group) => group.items.length > 0)
+          : []
 
       return {
         key: categoryKey(category.id),