Practice: File Upload Server

Build an Express server that:

1. Accepts a POST /upload request with a JSON body { "filename": "...", "content": "..." }

2. Writes the content to a file at /tmp/<filename>

3. Responds with { "saved": true, "path": "/tmp/<filename>" }

4. Returns { "error": "Missing filename or content" } with status 400 if either field is missing

5. Prints "Upload server ready" when the server starts, then closes

Focus on: JSON body parsing, input validation, fs.writeFileSync, and correct HTTP status codes.

Build an Express server that:

1. Accepts a POST /upload request with a JSON body { "filename": "...", "content": "..." }

2. Writes the content to a file at /tmp/<filename>

3. Responds with { "saved": true, "path": "/tmp/<filename>" }

4. Returns { "error": "Missing filename or content" } with status 400 if either field is missing

5. Prints "Upload server ready" when the server starts, then closes

Focus on: JSON body parsing, input validation, fs.writeFileSync, and correct HTTP status codes.