Refactor Knob component styles for performance

[MaddipatlaChetan24]

Fixes #1, Fixes #2

Description

Refactors two style overrides in the Knob component to use static,
module-level objects instead of inline object/function literals that
were being re-created on every render.

• RadioGroupRoot's style was written as a function
  (({ $theme }) => ({...})) but never actually referenced $theme in
  its return value — it was a constant disguised as a function. Replaced
  with a plain module-level RADIO_GROUP_ROOT_OVERRIDE_STYLE object,
  which baseui's overrides.<Component>.style accepts directly. This
  removes both the per-render function allocation and the function call
  baseui previously had to make to resolve it.
• The Checkbox's Label override (style: { fontWeight: 500 }) was
  already a static shape but was being re-allocated as a new object
  literal on every render. Hoisted to a module-level
  CHECKBOX_LABEL_OVERRIDE_STYLE constant so the same object reference
  is reused across renders.

Both changes are behavior-identical — same resolved styles, same visual
output — just without the unnecessary re-allocation.

Left the two per-Radio overrides inside the enum options .map()
unchanged. They do use $theme and can't become plain objects, and
while they could in principle also be hoisted to module scope, doing so
risks losing baseui's contextual type inference for the $theme
parameter (which is currently inferred from the JSX prop's expected
type) and could introduce a type error without knowing this project's
exact tsconfig/baseui override type setup. Flagging as a possible
follow-up rather than guessing at a fix that might not compile.

Scope

Patch: Bug Fix

[MaddipatlaChetan24]

can you please check this !!