fix(editor): image upload dialog polish and paste interceptor cleanup

- Remove image border from embed/login preview dialogs (dark theme fix)
- Use DOM paste listener instead of modifying ChangeHelper interceptor
- Add IMAGE_UPLOAD_UNSUPPORTED_TYPE and IMAGE_UPLOAD_LIMIT_TITLE strings
- Use uploading.svg placeholder during upload
- Fix language check to include gfm

Author: abose

src/editor/EditorCommandHandlers.js

@@ -1352,7 +1352,7 @@ define(function (require, exports, module) {
                 const loginHTML = `<div>
                     <p>${Strings.IMAGE_UPLOAD_LOGIN_REQUIRED_MSG}</p>
                     <div style="text-align: center;">
-                        <img src="${previewURL}" style="max-width: 300px; max-height: 200px; border: 1px solid #ccc; border-radius: 4px; margin: 12px 0;" />
+                        <img src="${previewURL}" style="max-width: 300px; max-height: 200px; border-radius: 4px; margin: 12px 0;" />
                     </div>
                 </div>`;
                 const dialog = Dialogs.showModalDialog(

src/nls/root/strings.js

@@ -404,6 +404,7 @@ define({
     "IMAGE_UPLOAD_HOSTED_ON": "Images are hosted on user-cdn.phcode.site",
     "IMAGE_UPLOAD_BTN": "Upload & Embed",
     "IMAGE_UPLOAD_DONT_SHOW_AGAIN": "Always embed without asking",
+    "IMAGE_UPLOAD_UNSUPPORTED_TYPE": "Unsupported image type: {0}",
     "IMAGE_UPLOAD_LIMIT_TITLE": "Upload more images with Phoenix Pro",
     "IMAGE_SEARCH_LIMIT_TITLE": "Image search limit reached",
     "IMAGE_SEARCH_LIMIT_MESSAGE": "You’ve used all {0} image searches for this month.<br>Start a paid Phoenix Pro plan to remove trial limits and continue searching.",