Implement Secure Token Storage and Encryption

[zakkiyyat]

Description:
Encrypt and decrypt access/refresh tokens for each music provider.

Requirements:

• Use crypto module or secure lib (e.g., bcrypt, crypto-js)
• Encrypt before storing in DB
• Decrypt when making API calls

Acceptance Criteria:

• Tokens not stored in plaintext
• Tests verify encryption round-trip

[yasinmuhd]

Hi, I'm a beginner in backend development and would love to take on this task to learn and improve. I'm eager to contribute and open to feedback. Thanks for the opportunity