feat(roles): role CRUD screen (list + form name/description + view/edit/delete + bulk)

Per request:
- Migration: add nullable 'description' to the roles table.
- RoleManager Livewire component + view at /admin/roles:
  * Roles list table with per-row checkboxes for bulk selection (+ select-all)
    and a 'Delete selected' bulk action (protected roles skipped).
  * 'New role' opens a modal form with just Name + Description (and permission
    checkboxes to assign).
  * Per-row View / Edit / Delete buttons (View modal shows description,
    counts and assigned permissions).
- Admin role stays protected (no rename/delete/lose 'manage all').
- /admin/users links to the new Roles screen; the phase-1 permission matrix
  stays available via a 'Matrix view' link.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

routes/web.php

@@ -136,6 +136,7 @@ Route::get('/reports/dashboard', ReportsDashboard::class)->name('reports.dashboa
         Route::get('/users/create',       \App\Livewire\UserForm::class)->name('users.create');
         Route::get('/users/{user}',       \App\Livewire\UserView::class)->name('users.show');
         Route::get('/users/{user}/edit',  \App\Livewire\UserForm::class)->name('users.edit');
+        Route::get('/roles',               \App\Livewire\RoleManager::class)->name('roles');
         Route::get('/permissions',         \App\Livewire\RolePermissionManager::class)->name('permissions');
     });