Implement unified file editing for all non-media files

Major improvements:
- Remove separate view/edit modes - editing state can view content too
- Expand text editing support to ALL file types except media/binary files
- Add realistic undo functionality for copy/cut operations
- Implement moveSSHItem API for proper cross-directory file moves
- Add file existence checks to prevent copy failures
- Enhanced error logging with full command and path information

Key changes:
- FileWindow: Expand editable file types to exclude only media extensions
- FileViewer: Remove view mode toggle, direct editing interface
- Backend: Add moveItem API endpoint for cut operations
- Backend: Add file existence verification before copy operations
- Frontend: Complete undo system for copy (delete copied files) and cut (move back to original location)

File type handling:
- Media files (jpg, mp3, mp4, etc.) → Display only
- All other files → Direct text editing (js, py, txt, config files, unknown extensions)

🤖 Generated with Claude Code

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

src/ui/main-axios.ts

@@ -1178,6 +1178,29 @@ export async function renameSSHItem(
     return response.data;
   } catch (error) {
     handleApiError(error, "rename SSH item");
+    throw error;
+  }
+}
+
+export async function moveSSHItem(
+  sessionId: string,
+  oldPath: string,
+  newPath: string,
+  hostId?: number,
+  userId?: string,
+): Promise<any> {
+  try {
+    const response = await fileManagerApi.put("/ssh/moveItem", {
+      sessionId,
+      oldPath,
+      newPath,
+      hostId,
+      userId,
+    });
+    return response.data;
+  } catch (error) {
+    handleApiError(error, "move SSH item");
+    throw error;
   }
 }