Replaced *router.StandardBunRouterAdapter parameter with BunRouterHandler
interface to support both bunrouter.Router and bunrouter.Group types,
enabling route registration on router groups with path prefixes.
- Added BunRouterHandler interface
- Updated SetupBunRouterRoutes signature
- Updated ExampleBunRouterWithBunDB to use bunrouter.New() directly
- Added ExampleBunRouterWithGroup demonstrating group usage