feat: add cover image functionality for articles

- Implemented `resolveApiURL` function to handle various URL formats.
- Updated `ArticleDetail` and `UpdateArticleRequest` interfaces to include `cover_asset_url`.
- Enhanced `ArticleEditorView` to manage cover image uploads, including a new `CoverPickerModal` component.
- Added cover image requirements logic in `cover-requirements.ts` to enforce platform-specific cover image rules.
- Modified backend services to handle cover image uploads and validations, including checks for required cover images for specific platforms.
- Improved error handling for cover image requirements during article publishing.

server/internal/tenant/app/media_service.go

@@ -456,6 +456,9 @@ func (s *MediaService) CreatePublishBatch(ctx context.Context, articleID int64,
 	if err != nil {
 		return nil, err
 	}
+	if publishBatchRequiresCover(accountSeeds) && strings.TrimSpace(pointerStringValue(req.CoverAssetURL)) == "" {
+		return nil, response.ErrBadRequest(40044, "publish_cover_required", "baijiahao publishing requires a cover image")
+	}
 
 	var publishBatchID int64
 	if err := tx.QueryRow(ctx, `
@@ -529,6 +532,22 @@ func (s *MediaService) CreatePublishBatch(ctx context.Context, articleID int64,
 	}, nil
 }
 
+func publishBatchRequiresCover(accounts []platformAccountSeed) bool {
+	for _, account := range accounts {
+		if strings.TrimSpace(account.PlatformID) == "baijiahao" {
+			return true
+		}
+	}
+	return false
+}
+
+func pointerStringValue(value *string) string {
+	if value == nil {
+		return ""
+	}
+	return *value
+}
+
 func (s *MediaService) ListArticlePublishRecords(ctx context.Context, articleID int64) ([]PublishRecordResponse, error) {
 	actor := auth.MustActor(ctx)
 	return s.listArticlePublishRecords(ctx, actor.TenantID, articleID)