Feat: Implement accepted token list API

[jaykayudo]

Description

This PR introduces an API endpoint that retrieves a list of all accepted Tokens, including their contract address, name, and the total number of active listings associated with each token contract address. The implementation uses Django's ModelSerializer to serialize the AcceptedToken model and efficiently aggregates the listing count using a custom method.

Related Issue

Fixes #9

Type of Change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• Performance improvement
• Code refactoring
• Documentation update
• Test coverage improvement
• CI/CD related changes

How Has This Been Tested?

• Unit tests
• Integration tests
• Manual testing

Checklist

• My code follows the project's style guidelines
• 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 new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

Security Considerations

• This PR introduces no security concerns
• This PR modifies authentication/authorization
• This PR handles sensitive data
• This PR modifies financial transaction logic

Performance Impact

• This PR has no significant performance impact
• This PR improves performance
• This PR may impact performance negatively (explain why it's necessary)

Additional Context