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/article_service.go

@@ -263,6 +263,7 @@ type ArticleDetailResponse struct {
 	TemplateName           *string                `json:"template_name"`
 	GenerationMode         *string                `json:"generation_mode"`
 	Platforms              []string               `json:"platforms"`
+	CoverAssetURL          *string                `json:"cover_asset_url"`
 	GenerateStatus         string                 `json:"generate_status"`
 	PublishStatus          string                 `json:"publish_status"`
 	Title                  *string                `json:"title"`
@@ -310,6 +311,7 @@ func (s *ArticleService) Detail(ctx context.Context, id int64) (*ArticleDetailRe
 	}
 	d.GenerationMode = resolveArticleGenerationMode(dbSourceType, inputParamsJSON)
 	d.Platforms = resolveArticlePlatforms(wizardStateJSON, inputParamsJSON)
+	d.CoverAssetURL = resolveArticleCoverAssetURL(wizardStateJSON)
 	d.WordCount = resolveWordCount(d.MarkdownContent, d.WordCount)
 	return &d, nil
 }
@@ -366,6 +368,7 @@ type UpdateArticleRequest struct {
 	Title           string   `json:"title"`
 	MarkdownContent string   `json:"markdown_content"`
 	Platforms       []string `json:"platforms"`
+	CoverAssetURL   *string  `json:"cover_asset_url"`
 }
 
 type ArticleImageUploadResponse struct {
@@ -418,7 +421,7 @@ func (s *ArticleService) Update(ctx context.Context, id int64, req UpdateArticle
 
 	wordCount := countArticleWords(markdown)
 	sourceLabel := "手动编辑"
-	nextWizardStateJSON, err := mergeArticleWizardState(wizardStateJSON, title, req.Platforms)
+	nextWizardStateJSON, err := mergeArticleWizardState(wizardStateJSON, title, req.Platforms, req.CoverAssetURL)
 	if err != nil {
 		return nil, response.ErrInternal(50012, "update_failed", "failed to update article metadata")
 	}