P2: Standardize auth to JWT (deprecate phpPassword)

[Kinin-Code-Offical]

Authentication is inconsistent, using both phpPassword and some JWT logic. All endpoints must be standardized to use JWT.

Acceptance Criteria:

• Create a reusable �uth_check.php that validates a Bearer token.
• Refactor all protected endpoints to use this auth check.
• Completely remove the phpPassword check from all endpoints.
• Update the Flutter HttpWrapper to only send the JWT Authorization header and not the phpPassword.