refactor: remove FFmpeg dependencies and related video processing logic

- Deleted FFmpeg related packages from package.json and package-lock.json.
- Removed video transcoding and editing functionalities from FileContent.vue.
- Simplified video handling logic and error management in FileContent.vue.
- Added a clear button in MilkdownEditor.vue for clearing the editor content.
- Enhanced UniverPreview.vue to clear detached popups and mount nodes on destroy.
- Updated docBlockPlugin.ts to improve context handling for document blocks.
- Cleaned up vite.config.js by removing cross-origin isolation headers.

package.json

@@ -12,10 +12,6 @@
   },
   "dependencies": {
     "@blocknote/xl-docx-exporter": "^0.47.3",
-    "@ffmpeg/core": "^0.12.10",
-    "@ffmpeg/core-mt": "^0.12.10",
-    "@ffmpeg/ffmpeg": "^0.12.15",
-    "@ffmpeg/util": "^0.12.2",
     "@milkdown/core": "^7.18.0",
     "@milkdown/crepe": "^7.18.0",
     "@milkdown/kit": "^7.18.0",
@@ -37,6 +33,8 @@
     "mermaid": "^11.12.3",
     "pinia": "^2.3.1",
     "prismjs": "^1.29.0",
+    "tui-color-picker": "^2.2.8",
+    "tui-image-editor": "^3.15.3",
     "vue": "^3.5.24",
     "vue-router": "^4.6.4"
   },