feat: introduce module system and extract address book as first module (MODULAR-MONOLITH-V1-001)

Add a module kernel (ModuleManifest, ModuleRegistry) that allows modules to
contribute routes, UI slots, search providers, layout context, session
lifecycle, and permissions. Modules are activated via config/modules.php or
APP_ENABLED_MODULES env variable. Conflicts (duplicate routes, permissions,
slot keys) cause a fail-fast with a clear error message.

Extract the address book from hardcoded Core integration points into the
first module (modules/addressbook/). The module provides:
- Aside icon-bar tab + People panel via UI slot system
- Global search resource via AddressBookSearchProvider
- Layout context data via AddressBookLayoutProvider
- Session lifecycle via AddressBookSessionProvider

Core cleanup removes address-book hardcodings from SearchSqlResourceProvider,
SearchUiMetaProvider, SearchItemMapperProvider, appBuildLayoutNavContext(),
and the aside templates. Permissions (ADDRESS_BOOK_VIEW) and business logic
(AddressBookService) remain in Core as they gate general user visibility.

Includes 38 new tests (894 total), PHPStan level 5 clean, and architecture
tests verifying zero hardcoded address-book references in search/templates.

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

config/modules.php

@@ -0,0 +1,13 @@
+<?php
+
+/**
+ * Module activation configuration.
+ *
+ * Modules listed here are loaded at boot time. The APP_ENABLED_MODULES env
+ * variable (comma-separated) overrides this list when set.
+ *
+ * Each entry must match a directory name under modules/ containing a module.php manifest.
+ */
+return [
+    'enabled_modules' => ['addressbook'],
+];

config/router.php

@@ -1,5 +1,6 @@
 <?php
 
+use MintyPHP\App\Module\ModuleRegistry;
 use MintyPHP\Router;
 
 $routesFile = __DIR__ . '/routes.php';
@@ -17,3 +18,18 @@ if (is_array($routeDefinitions)) {
         }
     }
 }
+
+// ── Module routes ────────────────────────────────────────────────────
+// Module routes are merged after core routes. The ModuleRegistry is
+// available at this point because registerContainer.php runs before
+// config/router.php is included.
+if (function_exists('app') && app(ModuleRegistry::class) instanceof ModuleRegistry) {
+    $moduleRegistry = app(ModuleRegistry::class);
+    foreach ($moduleRegistry->getRoutes() as $route) {
+        $path = trim((string) $route['path']);
+        $target = trim((string) $route['target']);
+        if ($path !== '' && $target !== '') {
+            Router::addRoute($path, $target);
+        }
+    }
+}