refactor: reorganize app router routes (#310)

*Issue #, if available:*

*Description of changes:*

* move /settings/api-keys to /api-keys
* move /settings/prompt to /preferences


By submitting this pull request, I confirm that you can use, modify,
copy, and redistribute this contribution, under the terms of your
choice.

Author: tmokmss

packages/webapp/src/app/settings/api-keys/components/ApiKeyClientActions.tsx renamed to packages/webapp/src/app/api-keys/components/ApiKeyClientActions.tsx

@@ -75,7 +75,7 @@ export default function Header() {
 
                 <DropdownMenuSeparator />
                 <DropdownMenuItem asChild>
-                  <Link href="/settings/api-keys" className="w-full cursor-default flex items-center" prefetch={false}>
+                  <Link href="/api-keys" className="w-full cursor-default flex items-center" prefetch={false}>
                     <Key className="mr-2 h-4 w-4" />
                     <span>{t('apiKeys')}</span>
                   </Link>
@@ -100,7 +100,7 @@ export default function Header() {
                   </Link>
                 </DropdownMenuItem>
                 <DropdownMenuItem asChild>
-                  <Link href="/settings/prompt" className="w-full cursor-default flex items-center" prefetch={false}>
+                  <Link href="/preferences" className="w-full cursor-default flex items-center" prefetch={false}>
                     <Settings className="mr-2 h-4 w-4" />
                     <span>{t('preferences')}</span>
                   </Link>