feat: use credential management api

[boomzero]

Summary

• add helper functions to store, load, and clear credentials
• use Credential Management API to save, retrieve, and clear login data instead of plaintext localStorage
• wrap credential retrieval and storage in async contexts to avoid syntax errors

Testing

• npm test (fails: Error: no test specified)

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https://chatgpt.com/codex/tasks/task_e_68a417a979e08332b8d1408faef6f3ff

[boomzero]

Well, it works

[boomzero]

@langningchen @PythonSmall-Q Well this works, so merge?

[boomzero]

The behavior is a bit different though

[boomzero]

@langningchen @PythonSmall-Q Well this works, so merge?

You should test it to see if you like the new behavior

[boomzero]

btw completely AI generated

[langningchen]

Although I haven't tested it, I think it would be great if it could work!

[boomzero]

Well as I said, there is a change in behavior, so it probably should be tested

[boomzero]

Though perhaps I should merge it so that more people can test it