feat(auth): add the authentication foundation for Strata users

[alucero270]

feat(auth): add the authentication foundation for Strata users

Summary

Add the baseline authentication layer needed for identified user access to Strata.

Scope

• Files: authentication setup, API integration points, auth docs as needed
• Components: user authentication, session or token handling, identity foundation

Acceptance Criteria

• Strata supports an explicit authentication foundation for user identity
• authentication behavior is documented clearly enough to test and verify
• authentication can be added without bypassing source-scope requirements

Notes

• Keep this issue focused on authentication, not role enforcement