refactor: remove unused OpenAIOAuthOptions after Sora platform removal

The options parameter only served to switch between 'openai' and 'sora'
platforms. With Sora removed, the parameter is unnecessary.

frontend/src/composables/__tests__/useOpenAIOAuth.spec.ts

@@ -20,7 +20,7 @@ import { useOpenAIOAuth } from '@/composables/useOpenAIOAuth'
 
 describe('useOpenAIOAuth.buildCredentials', () => {
   it('should keep client_id when token response contains it', () => {
-    const oauth = useOpenAIOAuth({ platform: 'openai' })
+    const oauth = useOpenAIOAuth()
     const creds = oauth.buildCredentials({
       access_token: 'at',
       refresh_token: 'rt',
@@ -34,7 +34,7 @@ describe('useOpenAIOAuth.buildCredentials', () => {
   })
 
   it('should keep legacy behavior when client_id is missing', () => {
-    const oauth = useOpenAIOAuth({ platform: 'openai' })
+    const oauth = useOpenAIOAuth()
     const creds = oauth.buildCredentials({
       access_token: 'at',
       refresh_token: 'rt',

frontend/src/composables/useOpenAIOAuth.ts

@@ -24,11 +24,7 @@ export interface OpenAITokenInfo {
 
 export type OpenAIOAuthPlatform = 'openai'
 
-interface UseOpenAIOAuthOptions {
-  platform?: OpenAIOAuthPlatform
-}
-
-export function useOpenAIOAuth(_options?: UseOpenAIOAuthOptions) {
+export function useOpenAIOAuth() {
   const appStore = useAppStore()
   const endpointPrefix = '/admin/openai'