fix(audit): harden module isolation and fix post-extraction drift

Fix 5 broken FQCN references (runtime errors) where core pages referenced
non-existent MintyPHP\Service\Audit\AuditMetadataEnricher and SystemAuditService.
Add AuditMetadataEnricherInterface with NullAuditMetadataEnricher fallback so
deactivating the audit module no longer crashes core edit pages.

Move audit search resources from core Search*Provider files into the module
via a new AuditSearchResourceProvider implementing the existing
SearchResourceProvider contract. Add module-specific purge permissions
(audit.api.purge, audit.imports.purge) replacing core ABILITY_ADMIN_SETTINGS_UPDATE.

Also fixes: session key prefix convention, hardcoded English string, $_SERVER
superglobal fallback, and manifest schema drift (i18n_path, group in ui_slots).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

modules/audit/module.php

@@ -99,10 +99,18 @@ return [
             'key' => 'audit.system.purge',
             'description' => 'Purge system audit logs',
         ],
+        [
+            'key' => 'audit.api.purge',
+            'description' => 'Purge API audit logs',
+        ],
         [
             'key' => 'audit.imports.view',
             'description' => 'View import audit logs',
         ],
+        [
+            'key' => 'audit.imports.purge',
+            'description' => 'Purge import audit logs',
+        ],
         [
             'key' => 'audit.user_lifecycle.view',
             'description' => 'View user lifecycle audit logs',
@@ -178,7 +186,9 @@ return [
     'session_providers' => [],
 
     'event_listeners' => [],
-    'search_resources' => [],
+    'search_resources' => [
+        \MintyPHP\Module\Audit\Providers\AuditSearchResourceProvider::class,
+    ],
     'asset_groups' => [],
     'migrations_path' => 'db/updates',
     'i18n_path' => 'i18n',