fix(ui/auth): display correct Apple sign-in callback URL (#11439)

# Which Problems Are Solved

- Apple Sign-In uses a Form Post method to return the authorization
response, which ZITADEL handles at a specific endpoint ending in /form
for the login v1.
- The Console previously displayed the standard callback URL (without
`/form`), causing confusion and configuration errors..


# How the Problems Are Solved

- **Console**: Updated ProviderNextService to accept a suffix string . 
- **Console**: Updated ProviderAppleComponent to append the suffix to
the urls.


# Additional Changes
- Updated `docs/docs/guides/integrate/identity-providers/apple.mdx` to
explicitly state that the callback URL end with `/form`
- Updated `docs/docs/guides/integrate/login-ui/external-login.mdx` to
clarify the `/form` suffix requirement for Apple Sign-In in the hosted
login documentation.
# Additional Context
- fixes #11438

---------

Co-authored-by: Ramon <[email protected]>
Co-authored-by: Florian Forster <[email protected]>

console/src/app/modules/providers/provider-apple/provider-apple.component.ts

@@ -72,7 +72,7 @@ export class ProviderAppleComponent {
     this.service$,
   );
   public expandWhatNow$ = this.nextSvc.expandWhatNow(this.id$, this.activateLink$, this.justCreated$);
-  public copyUrls$ = this.nextSvc.callbackUrls();
+  public copyUrls$ = this.nextSvc.callbackUrls(true);
 
   constructor(
     private authService: GrpcAuthService,

console/src/app/modules/providers/provider-next/provider-next.service.ts

@@ -80,12 +80,12 @@ export class ProviderNextService {
     );
   }
 
-  callbackUrls(): Observable<CopyUrl[]> {
+  callbackUrls(formPost: boolean = false): Observable<CopyUrl[]> {
     return this.env.env.pipe(
       map((env) => [
         {
           label: 'Login V1 Callback URL',
-          url: `${env.issuer}/ui/login/login/externalidp/callback`,
+          url: `${env.issuer}/ui/login/login/externalidp/callback${formPost ? '/form' : ''}`,
         },
         {
           label: 'Login V2 Callback URL',