### What problem does this PR solve?

Add license statement.

### Type of change

- [x] Refactoring

Signed-off-by: Jin Hai <haijin.chn@gmail.com>

### What problem does this PR solve?

Add back beartype

### Type of change

- [x] Refactoring

* add front end code

* change licence

* rename web_server to API

* change name to web_server

* clean rust version project

* clean rust version project

* build python version rag-flow