Implement MvWeb.Authorization module with can?/3 and can_access_page?/2
functions for conditional rendering in LiveView templates.
- can?/3 supports both resource atoms and record structs with scope checking
- can_access_page?/2 checks page access permissions
- All functions use PermissionSets module for consistency with backend
- Graceful handling of nil users and invalid permission sets
- Comprehensive test coverage with 17 test cases
