Refactor: Convert Motors tab to Nuxt UI (betaflight#4997)

* Refactor: Convert Motors tab to Nuxt UI

Replace legacy gui_box/table layouts, native selects, Switchery toggle
checkboxes, and raw buttons with Nuxt UI components (UiBox, SettingRow,
USwitch, USelect, UButton, UInputNumber). Remove GUI.switchery() calls
and associated LESS styles. Save button turns green when changes exist.
Sensor axis values use fixed-width for stable layout. All composables
and MSP logic unchanged.

Resolves part of betaflight#4995

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* Changes per review Vitroid

* Changes per review Coderabbit

* Use USlider

* Fix type mismatch for dshot_bidir

* Sanitize graph elements

* Improve styling

* Refactor meter bars to use UProgress

* Improve

* Remove lag on UProgress meter bar

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Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: haslinghuis