Replace the per-platform native form POST + manual CSRF + JSON/Blade
popup callback with a single Inertia mechanism:
- popupCallback() renders the accounts/PopupCallback Inertia page (notifies
the opener + closes the popup) for both the GET OAuth callbacks and the
selection submits. Drops the auth.social-callback Blade view, the
expectsJson JSON branch, and useHttp/useSocialConnect on the frontend.
- Selection/credential pages (LinkedIn, Facebook, Instagram, Bluesky,
Mastodon) use Inertia useForm: automatic CSRF + native validation errors.
- Unify the three selection screens on one row + View/Choose layout; the
LinkedIn company tag now uses a building icon.
- Bluesky auth failures throw ValidationException (422 for XHR, redirect
back with errors otherwise).
Controller tests updated from assertViewIs/assertViewHas to assertInertia.
cd2798fd8d