Add named session configuration profiles

[PurpleSentinel]

Parent: #23

Summary

Let users save and recall combinations of track duration, rest duration, launch sensitivity, warning settings, and display preferences for different events or drivers.

Acceptance criteria

• Create, rename, select, and delete profiles without corrupting the active settings.
• Show the active profile on the Ready screen.
• Define a safe default profile and migration for current user settings.
• Limit profile count and name length for RP2040 storage and display constraints.
• Cover profile lifecycle and recovery behavior with host tests.

Roadmap group

Session workflow and timing