fix: scanner wire:ignore + Company custom columns

- Scanner page: wrap the html5-qrcode camera container (#reader) in
  wire:ignore so a Livewire DOM morph can't tear down the live camera
  stream (same class of bug as the calendar).
- Company::getCustomColumns(): add `is_demo` and `default_warehouse_id`.
  Stancl Tenant treats columns absent from this list as virtual `data` JSON
  attributes, so editing a company could move default_warehouse_id into data
  and null the real column — breaking WarehouseService::defaultWarehouse.

Full suite: 100 passed.

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

resources/views/filament/tenant/pages/scanner.blade.php

@@ -35,7 +35,9 @@
     </style>
 
     <div class="sc-wrap" x-data="scanner()" x-init="init()">
-        <div class="sc-cam">
+        {{-- wire:ignore: html5-qrcode injects the camera DOM here; keep
+             Livewire's morph away so an update doesn't tear down the stream. --}}
+        <div class="sc-cam" wire:ignore>
             <div id="reader"></div>
             <div class="placeholder" x-show="!running && !error" x-cloak>
                 Apasă „Pornește" pentru a deschide camera.