FEATURE: Comprehensive multimedia file handling with professional components

- Integrated react-markdown with GitHub Flavored Markdown support
- Added react-pdf for PDF viewing with full navigation controls
- Implemented react-syntax-highlighter for code syntax highlighting
- Added dual-pane Markdown editor with live preview capability
- Fixed PDF.js worker configuration with local fallback
- Enhanced internationalization support for all multimedia controls
- Removed unsupported download buttons from Markdown editor
- Resolved version compatibility issues between PDF API and worker

技术改进 Claude Code生成

Co-Authored-By: Claude <noreply@anthropic.com>

src/locales/en/translation.json

@@ -668,6 +668,13 @@
     "connectToSsh": "Connect to SSH to use file operations",
     "uploadFile": "Upload File",
     "downloadFile": "Download",
+    "edit": "Edit",
+    "preview": "Preview",
+    "previous": "Previous",
+    "next": "Next",
+    "pageXOfY": "Page {{current}} of {{total}}",
+    "zoomOut": "Zoom Out",
+    "zoomIn": "Zoom In",
     "newFile": "New File",
     "newFolder": "New Folder",
     "rename": "Rename",