[Enhance] Add limiter & Building API

- Add a custom limiter and use it for limiting users' download instead of using database
> So add a requirement `limits`.

- Fix a character's value
- Change the email max length to 64
- Change something about API's roles and powers
- Add an API endpoint for getting users' roles and powers

README.md

@@ -99,7 +99,7 @@ It is just so interesting. What it can do is under exploration.
 ## 运行环境与依赖 Running environment and requirements
 - Windows/Linux/Mac OS/Android...
 - Python 3
-- Flask module >= 2.0, Cryptography module >= 35.0.0
+- Flask module >= 2.0, Cryptography module >= 35.0.0, limits >= 2.7.0
 - Charles, IDA, proxy app... (optional)
 
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