feat: module-owned i18n with merge-at-boot translation loading

Each module can now ship its own i18n/ directory with translation files
(default_de.json, default_en.json). At boot time, ModuleI18nLoader
preloads core translations then merges module translations on top via
Reflection into I18n::$strings — the t() helper stays unchanged.

- Add i18nPath property to ModuleManifest
- Add ModuleI18nLoader with Reflection-based preload
- Extract 59 module-exclusive keys from core i18n into module files
  (notifications: 8, bookmarks: 41, addressbook: 10)
- Expand TranslationKeysTest to scan modules/ and validate against
  merged core + module translations
- Add ModuleI18nContractTest for per-module de/en parity and completeness

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

modules/notifications/i18n/default_de.json

@@ -0,0 +1,10 @@
+{
+  "Notifications": "Benachrichtigungen",
+  "No notifications": "Keine Benachrichtigungen",
+  "Mark all as read": "Alle als gelesen markieren",
+  "Mark as read": "Als gelesen markieren",
+  "Dismiss": "Verwerfen",
+  "Action failed": "Aktion fehlgeschlagen",
+  "New user: %s": "Neuer Benutzer: %s",
+  "User deleted: %s": "Benutzer gelöscht: %s"
+}

modules/notifications/i18n/default_en.json

@@ -0,0 +1,10 @@
+{
+  "Notifications": "Notifications",
+  "No notifications": "No notifications",
+  "Mark all as read": "Mark all as read",
+  "Mark as read": "Mark as read",
+  "Dismiss": "Dismiss",
+  "Action failed": "Action failed",
+  "New user: %s": "New user: %s",
+  "User deleted: %s": "User deleted: %s"
+}

modules/notifications/module.php

@@ -0,0 +1,115 @@
+<?php
+
+/**
+ * Notifications module manifest.
+ *
+ * In-app notifications with bell icon, dropdown panel,
+ * event-driven creation, and scheduled cleanup.
+ */
+return [
+    'id' => 'notifications',
+    'version' => '1.0.0',
+    'enabled_by_default' => true,
+    'load_order' => 15,
+    'requires' => [],
+
+    'routes' => [
+        ['path' => 'notifications/list-data', 'target' => 'notifications/list-data'],
+        ['path' => 'notifications/mark-read-data', 'target' => 'notifications/mark-read-data'],
+        ['path' => 'notifications/delete-data', 'target' => 'notifications/delete-data'],
+        ['path' => 'notifications/unread-count-data', 'target' => 'notifications/unread-count-data'],
+    ],
+    'public_paths' => [],
+
+    'container_registrars' => [
+        \MintyPHP\Module\Notifications\NotificationsContainerRegistrar::class,
+    ],
+
+    'ui_slots' => [
+        'topbar.right_item' => [
+            [
+                'key' => 'notifications-bell',
+                'template' => 'templates/topbar-notification-bell.phtml',
+                'permission' => 'notifications.view',
+                'order' => 100,
+            ],
+        ],
+        'layout.head_style' => [
+            [
+                'key' => 'notifications-topbar-style',
+                'path' => 'modules/notifications/css/layout/app-topbar-notifications.css',
+                'permission' => 'notifications.view',
+                'order' => 100,
+            ],
+            [
+                'key' => 'notifications-dropdown-style',
+                'path' => 'modules/notifications/css/components/app-notification-dropdown.css',
+                'permission' => 'notifications.view',
+                'order' => 101,
+            ],
+        ],
+        'runtime.component' => [
+            [
+                'key' => 'notification-bell',
+                'script' => 'modules/notifications/js/components/app-notification-bell.js',
+                'export' => 'initNotificationBell',
+                'scope' => 'global',
+                'config_path' => 'components.notificationBell',
+                'default_config' => [],
+                'phase' => 'late',
+                'permission' => 'notifications.view',
+                'order' => 100,
+            ],
+        ],
+    ],
+
+    'authorization_policies' => [
+        \MintyPHP\Module\Notifications\NotificationsAuthorizationPolicy::class,
+    ],
+
+    'permissions' => [
+        [
+            'key' => 'notifications.view',
+            'label' => 'Notifications: View',
+            'description' => 'View and manage own notifications',
+        ],
+    ],
+
+    'event_listeners' => [
+        'user.created' => [
+            ['class' => \MintyPHP\Module\Notifications\Listeners\UserCreatedNotificationListener::class, 'method' => 'handle'],
+        ],
+        'user.deleted' => [
+            ['class' => \MintyPHP\Module\Notifications\Listeners\UserDeletedNotificationListener::class, 'method' => 'handle'],
+        ],
+    ],
+
+    'scheduler_jobs' => [
+        [
+            'job_key' => 'notifications_cleanup',
+            'handler' => \MintyPHP\Module\Notifications\Handler\NotificationCleanupJobHandler::class,
+            'label' => 'Notification cleanup',
+            'description' => 'Purges read notifications older than 90 days',
+            'default_enabled' => 1,
+            'default_timezone' => 'UTC',
+            'default_schedule_type' => 'daily',
+            'default_schedule_interval' => 1,
+            'default_schedule_time' => '04:00',
+            'default_schedule_weekdays_csv' => null,
+            'default_catchup_once' => 1,
+            'allowed_schedule_types' => ['daily', 'weekly'],
+        ],
+    ],
+
+    'layout_context_providers' => [
+        \MintyPHP\Module\Notifications\Providers\NotificationsLayoutProvider::class,
+    ],
+    'session_providers' => [
+        \MintyPHP\Module\Notifications\Providers\NotificationsSessionProvider::class,
+    ],
+
+    'search_resources' => [],
+    'asset_groups' => [],
+    'migrations_path' => 'db/updates',
+    'i18n_path' => 'i18n',
+];