feat: add read-only System Info admin page with health checks and module inventory

New page at /admin/system-info with three tabs:
- Overview: PHP version, SAPI, environment, 6 health checks (DB, schema,
  storage, RBAC baseline, admin role, scheduler heartbeat)
- Modules: table of active modules with version, dependencies, permission count
- Permissions: active/inactive counts and per-source breakdown

Gated behind new system_info.view permission assigned to Admin role.
No mutations — purely diagnostic/observability.

Includes SystemHealthService, SystemInfoService, SystemHealthRepository
with interface, DI registration, i18n keys (de+en), idempotent DB update
script, and 17 new PHPUnit tests.

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

lib/App/Container/Registrars/AppServicesRegistrar.php

@@ -4,6 +4,7 @@ namespace MintyPHP\App\Container\Registrars;
 
 use MintyPHP\App\AppContainer;
 use MintyPHP\App\Container\ContainerRegistrar;
+use MintyPHP\App\Module\ModuleRegistry;
 use MintyPHP\Http\ApiSystemAuditReporter;
 use MintyPHP\Http\CookieStore;
 use MintyPHP\Http\CookieStoreInterface;
@@ -42,6 +43,9 @@ use MintyPHP\Service\Security\RateLimiterService;
 use MintyPHP\Service\Security\SecurityServicesFactory;
 use MintyPHP\Service\Settings\SettingsFrontendTelemetryGateway;
 use MintyPHP\Service\Stats\AdminStatsViewDataService;
+use MintyPHP\Service\System\SystemHealthService;
+use MintyPHP\Service\System\SystemInfoService;
+use MintyPHP\Repository\System\SystemHealthRepository;
 
 final class AppServicesRegistrar implements ContainerRegistrar
 {
@@ -50,6 +54,15 @@ final class AppServicesRegistrar implements ContainerRegistrar
         $container->set(AdminStatsViewDataService::class, static fn (AppContainer $c): AdminStatsViewDataService => new AdminStatsViewDataService(
             $c->get(AdminStatsRepository::class)
         ));
+        $container->set(SystemHealthRepository::class, static fn (): SystemHealthRepository => new SystemHealthRepository());
+        $container->set(SystemHealthService::class, static fn (AppContainer $c): SystemHealthService => new SystemHealthService(
+            $c->get(SystemHealthRepository::class)
+        ));
+        $container->set(SystemInfoService::class, static fn (AppContainer $c): SystemInfoService => new SystemInfoService(
+            $c->get(SystemHealthService::class),
+            $c->get(SystemHealthRepository::class),
+            $c->has(ModuleRegistry::class) ? $c->get(ModuleRegistry::class) : null
+        ));
         $container->set(SearchDataService::class, static fn (AppContainer $c): SearchDataService => new SearchDataService(
             $c->get(PermissionService::class),
             $c->get(UserTenantRepository::class),