updated: removed gradient from onboarding buttons (#5178)

Fixes #5168

- Added primaryInverted and primaryInvertedHover to design system.
- Changed primary button background with a gradient to inverted-flat for
both light and dark themes.
- Hover added to go lighter (consistent with tertiary color of +5 step
on GRAY_SCALE).
- Font color changed from primary to inverted.
- Modified button border from light to strong.

Two components are still utilizing the button with gradient background -
email and chrome extension.
Figma design guidelines show them to be inverted and flat (not
gradient).

- Should I change those as well?
- Should the gradient style be removed altogether after this has been
completed?

Co-authored-by: Henry Kim <henrykim@Henrys-iMac.local>

packages/twenty-front/src/modules/ui/theme/constants/BackgroundDark.ts

@@ -25,4 +25,6 @@ export const BACKGROUND_DARK = {
   overlay: RGBA(GRAY_SCALE.gray80, 0.8),
   radialGradient: `radial-gradient(50% 62.62% at 50% 0%, #505050 0%, ${GRAY_SCALE.gray60} 100%)`,
   radialGradientHover: `radial-gradient(76.32% 95.59% at 50% 0%, #505050 0%, ${GRAY_SCALE.gray60} 100%)`,
+  primaryInverted: GRAY_SCALE.gray20,
+  primaryInvertedHover: GRAY_SCALE.gray15,
 };

packages/twenty-front/src/modules/ui/theme/constants/BackgroundLight.ts

@@ -25,4 +25,6 @@ export const BACKGROUND_LIGHT = {
   overlay: RGBA(GRAY_SCALE.gray80, 0.8),
   radialGradient: `radial-gradient(50% 62.62% at 50% 0%, #505050 0%, ${GRAY_SCALE.gray60} 100%)`,
   radialGradientHover: `radial-gradient(76.32% 95.59% at 50% 0%, #505050 0%, ${GRAY_SCALE.gray60} 100%)`,
+  primaryInverted: GRAY_SCALE.gray60,
+  primaryInvertedHover: GRAY_SCALE.gray55,
 };