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.

apps/admin-web/src/i18n/messages/en-US.ts

@@ -427,8 +427,15 @@ const enUS = {
       platformsTitle: "Publish platforms",
       platformsHint: "This stays in sync with Media Management so you can edit the article's publish platforms directly.",
       coverTitle: "Cover image",
-      coverHint: "Upload a cover asset before publishing. This is local preview only for now.",
+      coverHint: "Off by default. Once uploaded, the cover is saved with the article.",
+      coverRequired: "Baijiahao is selected, so the cover image becomes required.",
       coverUpload: "Upload cover image",
+      coverReplace: "Choose again",
+      coverRemove: "Remove cover",
+      coverSaved: "Cover asset saved",
+      coverOff: "Cover image is currently off. Turn it on to upload and crop a cover asset.",
+      coverTagRequired: "Required",
+      coverTagOptional: "Optional",
       imagePrompt: "Enter image URL",
       tablePicker: {
         empty: "Drag to choose a table size",
@@ -566,7 +573,8 @@ const enUS = {
       platformsTitle: "Target platforms",
       platformsHint: "Previously selected and bound accounts are prefilled first. Unbound or locally unavailable platforms stay disabled.",
       coverTitle: "Cover image",
-      coverHint: "This version uses a cover asset URL. Upload and crop can be wired later.",
+      coverHint: "Off by default. Uploading opens the cover picker and cropper.",
+      coverUpload: "Upload cover image",
       coverPlaceholder: "Enter an optional cover asset URL",
       messages: {
         success: "{count} publish tasks submitted.",
@@ -574,6 +582,7 @@ const enUS = {
         partial: "Publish finished with {success} succeeded and {failed} failed.",
         partialTitle: "Partial publish failure",
         selectPlatform: "Choose at least one available platform first.",
+        coverRequired: "Baidu Baijiahao is selected. Please upload a cover image first.",
         failureTitle: "Publish failed",
         failureItem: "Publishing to [{platform}] failed: [{reason}]",
         unknownFailure: "Unknown error",
@@ -592,6 +601,46 @@ const enUS = {
       copySuccess: "Link copied.",
     },
   },
+  coverPicker: {
+    title: "Select cover image",
+    tabs: {
+      local: "Body / Local Upload",
+      ai: "AI Cover",
+    },
+    previewTitle: "Cover crop preview",
+    previewHintLocked: "Baijiahao is selected, so the cover will be exported as 16:9 when you confirm.",
+    previewHintFree: "There is no forced cover ratio right now. You can upload the original image directly or adjust framing before confirming.",
+    requirementsTitle: "Platform requirements",
+    requirementsHint: "Requirements switch automatically based on the selected publish platforms. Baijiahao is mandatory.",
+    recommendedRatio: "Recommended ratio",
+    recommendedSize: "Recommended size",
+    required: "Required",
+    optional: "Optional",
+    zoom: "Zoom",
+    fileLabel: "Current cover",
+    emptyTitle: "No publish platform selected",
+    emptyPlatforms: "Choose publish platforms first and each platform's cover requirements will appear here.",
+    emptyHint: "Supports PNG, JPG, GIF, and WebP up to 10MB.",
+    aiTitle: "AI cover is coming soon",
+    aiHint: "For now this flow supports local upload and cropping. AI cover generation can be plugged in here later.",
+    actions: {
+      upload: "Local upload",
+      reset: "Reset framing",
+      remove: "Remove cover",
+    },
+    notes: {
+      required: "This platform currently requires a cover image in the publish flow. Publishing is blocked until one is uploaded.",
+      optional: "This platform already supports standalone covers and reuses the current crop when publishing.",
+      unsupported: "This platform's current integration does not consume a standalone cover yet and falls back to body content or the platform default.",
+    },
+    messages: {
+      invalidType: "Only PNG, JPG, GIF, and WebP images are supported.",
+      tooLarge: "Image size cannot exceed 10MB.",
+      missingImage: "Select a cover image first.",
+      missingArticle: "The article is not ready yet. Refresh and try again.",
+      imageLoadFailed: "Failed to load the cover image. Please choose another image.",
+    },
+  },
   brands: {
     eyebrow: "Brand Library",
     title: "Brand Library",