Update tenant lifecycle tooling and retire docs/process

app/Models/Tenant.php

@@ -25,6 +25,9 @@ class Tenant extends Model
         'settings' => 'array',
         'notification_preferences' => 'array',
         'last_activity_at' => 'datetime',
+        'anonymized_at' => 'datetime',
+        'pending_deletion_at' => 'datetime',
+        'deletion_warning_sent_at' => 'datetime',
         'total_revenue' => 'decimal:2',
         'settings_updated_at' => 'datetime',
         'subscription_expires_at' => 'datetime',