Benchmark: run on 5 real open-source Flask repos

[Nehal-cell]

What

Run CodeMorph's Flask→FastAPI migration on 5 real open-source projects and document the results.

Candidate repos (all MIT licensed, Flask + tests)

• pallets/flask (official examples)
• gothinkster/realworld (Flask implementation)
• mjhea0/flaskr-tdd
• realpython/flask-by-example
• hack4impact/flask-base

Output

Add results to BENCHMARK.md:

Repo	Files	Pass rate (first attempt)	After retries

This becomes the credibility evidence linked from the README.