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

src/db/catalog.rs

@@ -181,19 +181,29 @@ fn build_section(
         }
     }
 
-    // 所有类型统一：分组是可选子容器，条目可以挂在分组，也可以直属分区
+    // 应用类：分区 → 分组 → 条目；海报 / 图文是平铺列表，分组不参与渲染
     let tags = load_tags(conn, &section.key)?;
-    object.insert(
-        "groups".into(),
-        build_groups(conn, section, view_mode, &tags)?,
-    );
-
-    let direct = load_node_entries(conn, &section.key)?;
-    let items = direct
-        .iter()
-        .map(|entry| item_for(entry, view_mode, &tags))
-        .collect::<Vec<_>>();
-    object.insert("items".into(), json!(items));
+    if view_mode == "apps" {
+        object.insert(
+            "groups".into(),
+            build_groups(conn, section, view_mode, &tags)?,
+        );
+        let direct = load_node_entries(conn, &section.key)?;
+        let items = direct
+            .iter()
+            .map(|entry| item_for(entry, view_mode, &tags))
+            .collect::<Vec<_>>();
+        object.insert("items".into(), json!(items));
+    } else {
+        object.insert("groups".into(), json!([]));
+        // 平铺：把（可能存在的）分组里的条目一起取出来，切换类型时不丢内容
+        let entries = load_section_entries(conn, &section.key)?;
+        let items = entries
+            .iter()
+            .map(|entry| item_for(entry, view_mode, &tags))
+            .collect::<Vec<_>>();
+        object.insert("items".into(), json!(items));
+    }
 
     Ok(Value::Object(object))
 }
@@ -341,8 +351,49 @@ fn insert_optional(object: &mut Map<String, Value>, key: &str, value: &Option<St
 ///
 /// 条目只存 `node_key`，所属分区由父节点推导：
 /// 父节点是分组就取它的 `parent_key`，父节点是分区就取它自己。
-fn load_node_entries(conn: &Connection, node_key: &str) -> Result<Vec<EntryRow>, StashError> {
+/// 取某个分区下的全部条目（含分组内的），海报 / 图文平铺用。
+fn load_section_entries(
+    conn: &Connection,
+    section_key: &str,
+) -> Result<Vec<EntryRow>, StashError> {
     let mut stmt = conn
+        .prepare(
+            "SELECT e.key, e.name, e.description, e.icon, e.href, e.cover,
+                    e.banner, e.badge, e.comment, e.summary, e.body, e.hot, e.views, e.likes
+             FROM entry e
+             JOIN node p ON p.key = e.node_key
+             WHERE COALESCE(p.parent_key, p.key) = ?1
+             ORDER BY e.sort, e.key",
+        )
+        .map_err(map_error)?;
+
+    let entries = stmt
+        .query_map([section_key], |row| {
+            Ok(EntryRow {
+                key: row.get(0)?,
+                name: row.get(1)?,
+                description: row.get(2)?,
+                icon: row.get(3)?,
+                href: row.get(4)?,
+                cover: row.get(5)?,
+                banner: row.get(6)?,
+                badge: row.get(7)?,
+                comment: row.get(8)?,
+                summary: row.get(9)?,
+                body: row.get(10)?,
+                hot: row.get(11)?,
+                views: row.get(12)?,
+                likes: row.get(13)?,
+            })
+        })
+        .map_err(map_error)?
+        .collect::<Result<Vec<_>, _>>()
+        .map_err(map_error)?;
+
+    Ok(entries)
+}
+
+fn load_node_entries(conn: &Connection, node_key: &str) -> Result<Vec<EntryRow>, StashError> {    let mut stmt = conn
         .prepare(
             "SELECT e.key, e.name, e.description, e.icon, e.href, e.cover,
                     e.banner, e.badge, e.comment, e.summary, e.body, e.hot, e.views, e.likes

src/db/categories.rs

@@ -361,17 +361,22 @@ pub fn create_group(conn: &mut Connection, section_id: &str, new: NewGroup) -> R
         return Err(StashError::InvalidDirectory("分组标题需为 1–40 个字".into()));
     }
 
-    let section_exists: Option<String> = conn
+    let view_mode: Option<String> = conn
         .query_row(
-            "SELECT key FROM node WHERE key = ?1 AND kind = 'section'",
+            "SELECT view_mode FROM node WHERE key = ?1 AND kind = 'section'",
             [section_id],
             |row| row.get(0),
         )
         .optional()
         .map_err(map_error)?;
 
-    if section_exists.is_none() {
+    let Some(view_mode) = view_mode else {
         return Err(StashError::NotFound(format!("分区不存在: {section_id}")));
+    };
+    if view_mode != "apps" {
+        return Err(StashError::InvalidDirectory(
+            "只有应用类分区可以添加分组".into(),
+        ));
     }
 
     let exists: i64 = conn
@@ -707,18 +712,21 @@ mod tests {
     }
 
     #[test]
-    fn groups_under_any_kind_of_section() {
+    fn groups_only_under_apps_sections() {
         let mut conn = db();
         create(&mut conn, section("films", "电影", "posters")).expect("应能创建");
-        create_group(
-            &mut conn,
-            "films",
-            NewGroup {
-                id: "g1".into(),
-                title: "片单".into(),
-            },
-        )
-        .expect("海报分区也应能建分组");
+        assert!(
+            create_group(
+                &mut conn,
+                "films",
+                NewGroup {
+                    id: "g1".into(),
+                    title: "片单".into()
+                }
+            )
+            .is_err(),
+            "海报 / 图文分区不提供分组"
+        );
     }
 
     #[test]