feat: implement onboarding wizard and fix help page navigation

Core Features:
- Add Quick Setup Wizard for new users with multi-step flow
- Implement distraction-free onboarding layout (no sidebar/header)
- Create OnboardingController API endpoint for saving settings
- Redirect new users to /setup automatically on first admin access

Onboarding Components:
- StepMode: Select between full/minimal store modes
- StepHomepage: Choose or auto-create homepage
- StepAppearance: Configure container width and primary color
- StepProgress: Visual progress indicator

Navigation & Routing:
- Fix Help page links to use react-router navigation (prevent full reload)
- Update onboarding completion redirect to /appearance/pages
- Add manual onboarding access via Settings > Store Details

UI/UX Improvements:
- Enable dark mode support for Page Editor
- Fix page title rendering in onboarding dropdown
- Improve title fallback logic (title.rendered, title, post_title)

Type Safety:
- Unify PageItem interface across all components
- Add 'default' to containerWidth type definition
- Add missing properties (permalink_base, has_template, icon)

Files Modified:
- includes/Api/OnboardingController.php
- includes/Api/Routes.php
- includes/Admin/Assets.php
- admin-spa/src/App.tsx
- admin-spa/src/routes/Onboarding/*
- admin-spa/src/routes/Help/DocContent.tsx
- admin-spa/src/routes/Settings/Store.tsx
- admin-spa/src/routes/Appearance/Pages/*

admin-spa/src/routes/Appearance/Pages/components/InspectorPanel.tsx

@@ -32,7 +32,7 @@ import {
 import { InspectorField, SectionProp } from './InspectorField';
 import { InspectorRepeater } from './InspectorRepeater';
 import { MediaUploader } from '@/components/MediaUploader';
-import { SectionStyles, ElementStyle } from '../store/usePageEditorStore';
+import { SectionStyles, ElementStyle, PageItem } from '../store/usePageEditorStore';
 
 interface Section {
     id: string;
@@ -44,17 +44,6 @@ interface Section {
     props: Record<string, SectionProp>;
 }
 
-interface PageItem {
-    id?: number;
-    type: 'page' | 'template';
-    cpt?: string;
-    slug?: string;
-    title: string;
-    url?: string;
-    isSpaLanding?: boolean;
-    containerWidth?: 'boxed' | 'fullwidth';
-}
-
 interface InspectorPanelProps {
     page: PageItem | null;
     selectedSection: Section | null;

admin-spa/src/routes/Appearance/Pages/components/PageSidebar.tsx

@@ -3,15 +3,7 @@ import { __ } from '@/lib/i18n';
 import { cn } from '@/lib/utils';
 import { FileText, Layout, Loader2, Home } from 'lucide-react';
 
-interface PageItem {
-    id?: number;
-    type: 'page' | 'template';
-    cpt?: string;
-    slug?: string;
-    title: string;
-    has_template?: boolean;
-    permalink_base?: string;
-}
+import { PageItem } from '../store/usePageEditorStore';
 
 interface PageSidebarProps {
     pages: PageItem[];

admin-spa/src/routes/Appearance/Pages/index.tsx

@@ -10,21 +10,7 @@ import { PageSidebar } from './components/PageSidebar';
 import { CanvasRenderer } from './components/CanvasRenderer';
 import { InspectorPanel } from './components/InspectorPanel';
 import { CreatePageModal } from './components/CreatePageModal';
-import { usePageEditorStore, Section } from './store/usePageEditorStore';
-
-// Types
-interface PageItem {
-    id?: number;
-    type: 'page' | 'template';
-    cpt?: string;
-    slug?: string;
-    title: string;
-    url?: string;
-    icon?: string;
-    has_template?: boolean;
-    permalink_base?: string;
-    isFrontPage?: boolean;
-}
+import { usePageEditorStore, Section, PageItem } from './store/usePageEditorStore';
 
 export default function AppearancePages() {
     const queryClient = useQueryClient();
@@ -229,12 +215,12 @@ export default function AppearancePages() {
     return (
         <div className={
             cn(
-                "flex flex-col bg-white transition-all duration-300",
+                "flex flex-col bg-background transition-all duration-300",
                 isFullscreen ? "fixed inset-0 z-[100] h-screen" : "h-[calc(100vh-64px)]"
             )
         } >
             {/* Header */}
-            < div className="flex items-center justify-between px-6 py-3 border-b bg-white" >
+            < div className="flex items-center justify-between px-6 py-3 border-b bg-background" >
                 <div>
                     <h1 className="text-xl font-semibold">{__('Page Editor')}</h1>
                     <p className="text-sm text-muted-foreground">
@@ -315,7 +301,7 @@ export default function AppearancePages() {
                             }
                         />
                     ) : (
-                        <div className="flex-1 bg-gray-100 flex items-center justify-center text-gray-400">
+                        <div className="flex-1 bg-muted/30 flex items-center justify-center text-muted-foreground">
                             <div className="text-center">
                                 <Layout className="w-16 h-16 mx-auto mb-4 opacity-50" />
                                 <p className="text-lg">{__('Select a page from the sidebar')}</p>

admin-spa/src/routes/Appearance/Pages/store/usePageEditorStore.ts

@@ -60,9 +60,12 @@ export interface PageItem {
     slug?: string;
     title: string;
     url?: string;
+    icon?: string;
+    has_template?: boolean;
+    permalink_base?: string;
     isFrontPage?: boolean;
     isSpaLanding?: boolean;
-    containerWidth?: 'boxed' | 'fullwidth';
+    containerWidth?: 'boxed' | 'fullwidth' | 'default';
 }
 
 interface PageEditorState {