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>

.agents/contracts/module-manifest.schema.json

@@ -89,7 +89,8 @@
               "order": { "type": "integer", "default": 100 },
               "details_storage": { "type": "string" },
               "details_open_active": { "type": "boolean" },
-              "base_url": { "type": "string" }
+              "base_url": { "type": "string" },
+              "group": { "type": "string", "description": "Sidebar nav group key for grouping related items under a details/summary section." }
             }
           }
         }
@@ -203,6 +204,11 @@
       "type": ["string", "null"],
       "description": "Relative path to SQL migration scripts. Resolved against module basePath.",
       "default": null
+    },
+    "i18n_path": {
+      "type": ["string", "null"],
+      "description": "Relative path to i18n translation files. Resolved against module basePath.",
+      "default": null
     }
   },
   "additionalProperties": false