Refactor routing to follow RR6 routing guidelines

[kurtdoherty]

Context

The template's example app does not leverage RR6's nested routing. Among other things, this prevents the ability to leverage RR6's route loaders.

Scope

• Refactor example pages to use RR6's nested routing.
• Restructure pages to encourage better domain boundaries.

Out-of-scope

The following changes have been explicitly de-scoped for now:

• Refactoring of data loading architecture to reduce request waterfalls;
• Use of route loaders to initiative retrieval of page data early.