feat(help-center): add help panel to sidebar icon bar

New help-center module adds a question-mark icon to the sidebar with
an aside panel containing three sections: Documentation (permission-
gated links to docs viewer and API docs), Keyboard Shortcuts (inline
reference from HotkeyService with Mac/Win variants), and About
(application info). Visible to all logged-in users — individual
resource links respect existing permissions.

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

modules/help-center/module.php

@@ -0,0 +1,54 @@
+<?php
+
+/**
+ * Help Center module manifest.
+ *
+ * Adds a help icon to the sidebar with documentation links,
+ * keyboard shortcuts reference, and system information.
+ */
+return [
+    'id' => 'help-center',
+    'version' => '1.0.0',
+    'enabled_by_default' => true,
+    'load_order' => 30,
+    'requires' => [],
+
+    'routes' => [],
+    'public_paths' => [],
+    'container_registrars' => [
+        \MintyPHP\Module\HelpCenter\HelpCenterContainerRegistrar::class,
+    ],
+
+    'ui_slots' => [
+        'aside.tab_panel' => [
+            [
+                'key' => 'help',
+                'label' => 'Help',
+                'icon' => 'bi-question-circle',
+                'href' => '',
+                'permission' => '',
+                'panel_template' => 'templates/aside-help-panel.phtml',
+                'order' => 900,
+            ],
+        ],
+        'layout.head_style' => [
+            [
+                'key' => 'help-center-style',
+                'path' => 'modules/help-center/css/components/app-help-panel.css',
+                'order' => 200,
+            ],
+        ],
+    ],
+
+    'authorization_policies' => [],
+    'search_resources' => [],
+    'asset_groups' => [],
+    'scheduler_jobs' => [],
+    'layout_context_providers' => [],
+    'session_providers' => [],
+    'permissions' => [],
+    'event_listeners' => [],
+    'deactivation_handler' => null,
+    'migrations_path' => null,
+    'i18n_path' => 'i18n',
+];