feat: add media upload to news editor with drag-drop, paste, and file picker

Upload images/videos directly to server from editor. DOMPurify video
sanitization, XSS protection, upload cancellation on unmount.

src/locales/en.json

@@ -4509,6 +4509,11 @@
       "saved": "Article saved",
       "deleted": "Article deleted",
       "selectColor": "Select color {{color}}",
+      "uploading": "Uploading...",
+      "dropMedia": "Drop image or video here",
+      "uploadError": "Upload failed",
+      "fileTooLarge": "File is too large",
+      "uploadFeaturedImage": "Upload image",
       "toolbar": {
         "bold": "Bold",
         "italic": "Italic",

src/locales/fa.json

@@ -3957,6 +3957,11 @@
       "saved": "مقاله ذخیره شد",
       "deleted": "مقاله حذف شد",
       "selectColor": "انتخاب رنگ {{color}}",
+      "uploading": "در حال آپلود...",
+      "dropMedia": "تصویر یا ویدیو را اینجا رها کنید",
+      "uploadError": "آپلود ناموفق بود",
+      "fileTooLarge": "فایل خیلی بزرگ است",
+      "uploadFeaturedImage": "آپلود تصویر",
       "toolbar": {
         "bold": "پررنگ",
         "italic": "کج",

src/locales/ru.json

@@ -5076,6 +5076,11 @@
       "saved": "Новость сохранена",
       "deleted": "Новость удалена",
       "selectColor": "Выбрать цвет {{color}}",
+      "uploading": "Загрузка...",
+      "dropMedia": "Перетащите изображение или видео сюда",
+      "uploadError": "Ошибка загрузки",
+      "fileTooLarge": "Файл слишком большой",
+      "uploadFeaturedImage": "Загрузить изображение",
       "toolbar": {
         "bold": "Жирный",
         "italic": "Курсив",

src/locales/zh.json

@@ -3956,6 +3956,11 @@
       "saved": "文章已保存",
       "deleted": "文章已删除",
       "selectColor": "选择颜色 {{color}}",
+      "uploading": "上传中...",
+      "dropMedia": "将图片或视频拖到这里",
+      "uploadError": "上传失败",
+      "fileTooLarge": "文件太大",
+      "uploadFeaturedImage": "上传图片",
       "toolbar": {
         "bold": "粗体",
         "italic": "斜体",