Basic Python CSV Data Cleaner

I have a small CSV file that needs a quick clean-up using nothing more than the Python standard library. The task is to write a single, well-commented .py script that

• reads the original CSV,
• applies a handful of common cleaning actions (duplicate removal, simple missing-value handling, trimming stray whitespace, and normalising line endings), all driven by clear function calls or flags so I can switch steps on or off later, and
• writes the result to a new file while preserving the original column order.

Please keep external dependencies out of the solution—csv, re, datetime or similar built-ins are fine, but no pandas or third-party packages. A short README or docstring showing command-line usage is all the documentation I need.

Acceptance: running “python clean.py input.csv output.csv” on my machine (Python 3.10) completes without errors and the output file reflects the cleaning steps above.