Restrict document edit/delete to owners and close public registration

Adds DocumentPolicy gating update/delete to the creator (admins bypass via
before()), invokes $this->authorize() in DocumentEditor mount/save/delete,
applies can:update,document on the edit route, hides the edit button for
non-owners, and removes the open /register routes so accounts must be
provisioned via the admin panel.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/resources/views/livewire/document-viewer.blade.php

@@ -6,7 +6,7 @@
                 {{ $document->title }}
             </h1>
 
-            @auth
+            @can('update', $document)
                 <a
                     href="{{ route('documents.edit', $document) }}"
                     class="inline-flex items-center justify-center px-3 sm:px-4 py-2 bg-indigo-600 text-white text-sm font-medium rounded-md hover:bg-indigo-700 focus:outline-none focus:ring-2 focus:ring-offset-2 focus:ring-indigo-500 whitespace-nowrap"
@@ -16,7 +16,7 @@ class="inline-flex items-center justify-center px-3 sm:px-4 py-2 bg-indigo-600 t
                     </svg>
                     {{ __('messages.documents.edit') }}
                 </a>
-            @endauth
+            @endcan
         </div>
 
         <div class="flex flex-col sm:flex-row sm:items-center text-xs sm:text-sm text-gray-500 gap-2 sm:gap-4">