feat: add content management feature for superadmin

- Implemented API endpoint for fetching content list with filtering, sorting, and pagination.
- Added DTOs for content items and tenant information.
- Created frontend components for content management, including search and data table functionalities.
- Updated routing to include content management page.
- Enhanced the superadmin menu to navigate to the new content management section.
- Included necessary styles and scripts for the new content management interface.

backend/docs/swagger.yaml

@@ -651,6 +651,30 @@ definitions:
         description: Order is the created or existing order record (may be nil for
           owner/free-path without order).
     type: object
+  dto.SuperContentItem:
+    properties:
+      content:
+        $ref: '#/definitions/models.Content'
+      owner:
+        $ref: '#/definitions/dto.SuperUserLite'
+      price:
+        $ref: '#/definitions/models.ContentPrice'
+      status_description:
+        type: string
+      tenant:
+        $ref: '#/definitions/dto.SuperContentTenantLite'
+      visibility_description:
+        type: string
+    type: object
+  dto.SuperContentTenantLite:
+    properties:
+      code:
+        type: string
+      id:
+        type: integer
+      name:
+        type: string
+    type: object
   dto.SuperOrderDetail:
     properties:
       buyer:
@@ -1557,6 +1581,109 @@ paths:
             $ref: '#/definitions/dto.LoginResponse'
       tags:
       - Super
+  /super/v1/contents:
+    get:
+      consumes:
+      - application/json
+      parameters:
+      - description: Asc specifies comma-separated field names to sort ascending by.
+        in: query
+        name: asc
+        type: string
+      - in: query
+        name: created_at_from
+        type: string
+      - in: query
+        name: created_at_to
+        type: string
+      - description: Desc specifies comma-separated field names to sort descending
+          by.
+        in: query
+        name: desc
+        type: string
+      - in: query
+        name: id
+        type: integer
+      - in: query
+        name: keyword
+        type: string
+      - description: Limit is page size; only values in {10,20,50,100} are accepted
+          (otherwise defaults to 10).
+        in: query
+        name: limit
+        type: integer
+      - description: Page is 1-based page index; values <= 0 are normalized to 1.
+        in: query
+        name: page
+        type: integer
+      - in: query
+        name: price_amount_max
+        type: integer
+      - in: query
+        name: price_amount_min
+        type: integer
+      - in: query
+        name: published_at_from
+        type: string
+      - in: query
+        name: published_at_to
+        type: string
+      - enum:
+        - draft
+        - reviewing
+        - published
+        - unpublished
+        - blocked
+        in: query
+        name: status
+        type: string
+        x-enum-varnames:
+        - ContentStatusDraft
+        - ContentStatusReviewing
+        - ContentStatusPublished
+        - ContentStatusUnpublished
+        - ContentStatusBlocked
+      - in: query
+        name: tenant_code
+        type: string
+      - in: query
+        name: tenant_id
+        type: integer
+      - in: query
+        name: tenant_name
+        type: string
+      - in: query
+        name: user_id
+        type: integer
+      - in: query
+        name: username
+        type: string
+      - enum:
+        - public
+        - tenant_only
+        - private
+        in: query
+        name: visibility
+        type: string
+        x-enum-varnames:
+        - ContentVisibilityPublic
+        - ContentVisibilityTenantOnly
+        - ContentVisibilityPrivate
+      produces:
+      - application/json
+      responses:
+        "200":
+          description: OK
+          schema:
+            allOf:
+            - $ref: '#/definitions/requests.Pager'
+            - properties:
+                items:
+                  $ref: '#/definitions/dto.SuperContentItem'
+              type: object
+      summary: 内容列表（平台侧汇总）
+      tags:
+      - Super
   /super/v1/orders:
     get:
       consumes: