Create internal/router/ package to organize route registration:
- router.go: Main router setup and configuration
- auth.go: Authentication routes (login, register, profile, etc.)
- docs.go: Documentation routes
- frontend.go: Frontend SSR routes (/, /login, /admin, etc.)
- helpers.go: Helper functions for template rendering
This is the first step in refactoring 858-line main.go into
a more maintainable structure following Go best practices.
Routes themselves have NOT changed - only organization.
