Improve speaker invites and redesign roster add flow.

Surface specific send failures, allow resend, use ladl.link portal URLs, and replace stacked speaker forms with a single add-to-list pattern.

Co-authored-by: Cursor <cursoragent@cursor.com>

app/Http/Controllers/Events/SpeakerController.php

@@ -90,10 +90,13 @@ class SpeakerController extends Controller
             'email' => ['required', 'email', 'max:190'],
         ]);
 
-        $sent = $this->invites->sendManualInvite($event, $event->user, $validated['email']);
+        $owner = ladill_account() ?? $event->user;
+        abort_unless($owner, 500);
 
-        if (! $sent) {
-            return back()->with('error', 'Could not send invitation. Check the email address or whether this speaker was already invited from the programme.');
+        $result = $this->invites->sendManualInvite($event, $owner, $validated['email']);
+
+        if (! $result['ok']) {
+            return back()->with('error', $result['error']);
         }
 
         return back()->with('success', 'Speaker invitation sent.');