Add screenshot auth middleware, remove SupportPal references

Screenshot auth: dev-only middleware that authenticates headless Chrome
via ?_screenshot_token= query param. Auto-selects admin/customer user
by subdomain. Only active when APP_ENV=local or explicitly enabled.

SupportPal cleanup: dropped supportpal_ticket_id column, removed env
vars and Phase 7 task tracking. 7 new tests (151 total, 782 assertions).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

website/app/Models/SupportTicket.php

@@ -15,7 +15,6 @@ class SupportTicket extends Model
 
     protected $fillable = [
         'user_id',
-        'supportpal_ticket_id',
         'subject',
         'status',
         'priority',
@@ -27,7 +26,6 @@ class SupportTicket extends Model
     protected function casts(): array
     {
         return [
-            'supportpal_ticket_id' => 'integer',
             'last_reply_at' => 'datetime',
         ];
     }