Auth system for `create blogs` endpoint

[Harshal141]

To maintain the integrity and scalability of the platform, all newly created blogs must be submitted by authenticated users.

Goals:
✅ Reduce spam and ensure only verified users can create blogs.
✅ Ensure the authentication system works both locally and in production environments.
✅ Keep the system open source friendly — contributors should be able to run and test it easily without being blocked by auth restrictions.

Suggested Solution:
We recommend using SuperTokens to implement a simple, scalable authentication layer. It supports GitHub login out-of-the-box and can be self-hosted for full control, making it ideal for open source ecosystems.

NOTE: self-hosting is not needed currently, and is not included in this issue's scope.