Refactor: footswitch init and add tests

[sastraxi]

Renames Footswitch.enabled to toggled throughout the codebase. The old name was misleading as it tracked the toggle state of the switch (on/off), not whether the switch itself was enabled.

Disambiguating this frees us up to do the following:

• disable: true already suppresses a footswitch for a given pedalboard; we now save its current value in the Footswitch object
• longpress on an encoder now works the same way it already did on footswitches — pedalboard config can override the default callback, and an explicit null clears it. Required threading encoder GPIO switches through a new encoder_switch_map keyed by config id, populated by pistomptre at init.

Tests in tests/v3/test_hardware_config.py cover both the existing footswitch overlay behaviour (longpress set/override/reset/suppress, color persistence) and the new encoder + disable paths.

The pistompcore encoder init still hardcodes a single switch; added a brief XXX comment about it.

[rreichenbach]

This looks good and seems to work well.