Auth Improvements + env template

[MyDrift-user]

Type of Change

• New feature
• Security patch
• UI/UX improvement

Description

• Introduced a .env.example file for environment configuration guidance.
• Updated requirements.txt to include itsdangerous.
• Enhanced FastAPI app to attach HTTP Bearer security to all endpoints except /auth for Swagger token propagation.
• Refactored token extraction in utils.py to support both Authorization header and query parameter, and updated handler signatures to include request for improved token resolution.

Testing

• tested, works

Checklist

• My code adheres to the coding and style guidelines of the project.
• I have performed a self-review of my own code.
• I have commented my code, particularly in hard-to-understand areas.
• I have made corresponding changes to the documentation.
• My changes generate no errors/warnings/merge conflicts.