[APP-1310] Button cleanup (#8754)

* Rm gradient buttons from Storybook

* TEMP move storybook button section

* Remove gradient_sky

* Remove actual defs for gradient_sky and gradient_primary

* Remove other gradient defs

* Remove gradient support entirely

* Deprecate 'variant' in favor of 'color'

* Fork base styles codepath to make variant deprecation more obvious

* Remove text styles for when no color is set, never been used

* Fork text styles codepath to make variant deprecation more obvious

* Revert temp storybook commit, remove deprecated values

* Replace remaining gradient button usage

src/screens/Onboarding/StepFinished.tsx

@@ -305,8 +305,8 @@ export function StepFinished() {
         <Button
           disabled={saving}
           key={state.activeStep} // remove focus state on nav
-          variant="gradient"
-          color="gradient_sky"
+          variant="solid"
+          color="primary"
           size="large"
           label={_(msg`Complete onboarding and start using your account`)}
           onPress={finishOnboarding}>

src/screens/Onboarding/StepInterests/index.tsx

@@ -15,7 +15,7 @@ import {
   TitleText,
 } from '#/screens/Onboarding/Layout'
 import {
-  ApiResponseMap,
+  type ApiResponseMap,
   Context,
   useInterestsDisplayNames,
 } from '#/screens/Onboarding/state'
@@ -235,8 +235,8 @@ export function StepInterests() {
         ) : (
           <Button
             disabled={saving || !data}
-            variant="gradient"
-            color="gradient_sky"
+            variant="solid"
+            color="primary"
             size="large"
             label={_(msg`Continue to next step`)}
             onPress={saveInterests}>

src/screens/Onboarding/StepProfile/index.tsx

@@ -267,8 +267,8 @@ export function StepProfile() {
         <OnboardingControls.Portal>
           <View style={[a.gap_md, gtMobile && {flexDirection: 'row-reverse'}]}>
             <Button
-              variant="gradient"
-              color="gradient_sky"
+              variant="solid"
+              color="primary"
               size="large"
               label={_(msg`Continue to next step`)}
               onPress={onContinue}>