Generate share passwords and offer them again beside the new link

Uploaders no longer have to make up a share password. With "Password
protect" on, the upload page has Generate and Copy under the field, and
the page the upload leads to offers the password once more beside the
link: masked, with the same copy button at the end of the field as the
link's. The password also derives the share's encryption key and only
its hash is stored, so a lost one means files nobody can open.

- PasswordGeneratorService draws from Random\Randomizer's secure engine.
  Characters are drawn uniformly and redrawn until every chosen set
  appears; passphrases come from EFF's large word list (CC BY 3.0 US,
  credited in the README), without its four hyphenated words.
- Admin settings gain a "Share Passwords" card: mode (off, on request,
  prefilled as protection is switched on), kind (characters: length
  12–64, the sets, look-alikes left out; passphrase: 4–10 words and a
  separator), and an example with its estimated entropy that follows the
  form before saving. Fields the chosen mode or kind hides are excluded
  from validation and keep their saved value. The default is on
  request, 20 letters and numbers without look-alikes.
- FileUploader flashes the password encrypted with the share's token;
  ShareCreated shows it only when the token matches, so a reload or any
  other visitor sees nothing. Crypt covers installs without
  SESSION_ENCRYPT, which the Docker setup does not set.
- The symbol set leaves out what chat apps turn into formatting and
  what breaks inside quotes, so a pasted password arrives unchanged.
- app.css imports group.css for <x-group>; .ai/rules/views.md records
  that <x-group> drops data-test and other attributes.
- Tests cover the generator, the admin card's saving, validation and
  example, prefill and generate on the upload page, the flash, and in
  Chromium Generate and Copy on the upload page and the masked copy on
  the share page. The admin settings page now has six headed sections.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

app/Livewire/FileUploader.php

@@ -3,7 +3,9 @@
 namespace App\Livewire;
 
 use App\Models\Setting;
+use App\Services\PasswordGeneratorService;
 use App\Services\ShareService;
+use Illuminate\Support\Facades\Crypt;
 use Illuminate\Support\Facades\Log;
 use Illuminate\Validation\ValidationException;
 use Livewire\Attributes\Layout;
@@ -101,6 +103,29 @@ class FileUploader extends Component
         }
     }
 
+    /**
+     * Fill in a generated password as protection is switched on, when the admin chose "Prefilled".
+     * A password already in the field stays.
+     */
+    public function updatedUsePassword(bool $value): void
+    {
+        $passwordGenerator = app(PasswordGeneratorService::class);
+
+        if ($value && $this->password === '' && $passwordGenerator->mode() === 'prefill') {
+            $this->password = $passwordGenerator->generate();
+        }
+    }
+
+    public function generatePassword(PasswordGeneratorService $passwordGenerator): void
+    {
+        if ($passwordGenerator->mode() === 'off') {
+            return;
+        }
+
+        $this->password = $passwordGenerator->generate();
+        $this->resetErrorBag('password');
+    }
+
     public function removeFile(int $index): void
     {
         unset($this->files[$index], $this->relativePaths[$index]);
@@ -184,6 +209,15 @@ class FileUploader extends Component
             'max_downloads' => $this->maxDownloads ?: null,
         ]);
 
+        // The page the upload leads to offers the password once more, next to the link; it is
+        // never stored in the clear, so this flash is the only way it gets there.
+        if ($this->usePassword) {
+            session()->flash('share_password', [
+                'token' => $share->token,
+                'password' => Crypt::encryptString($this->password),
+            ]);
+        }
+
         $this->redirect(route('share.created', $share), navigate: true);
     }
 
@@ -197,6 +231,7 @@ class FileUploader extends Component
             'siteDescription' => Setting::get('site_description'),
             'siteLogo' => Setting::get('site_logo'),
             'allowNeverExpire' => (bool) Setting::get('allow_never_expire', false),
+            'passwordGeneratorMode' => app(PasswordGeneratorService::class)->mode(),
         ]);
     }
 }