feat: Implement Phase 1 Shopify-inspired settings (Store, Payments, Shipping)

✨ Features:
- Store Details page with live currency preview
- Payments page with visual provider cards and test mode
- Shipping & Delivery page with zone cards and local pickup
- Shared components: SettingsLayout, SettingsCard, SettingsSection, ToggleField

🎨 UI/UX:
- Card-based layouts (not boring forms)
- Generous whitespace and visual hierarchy
- Toast notifications using sonner (reused from Orders)
- Sticky save button at top
- Mobile-responsive design

🔧 Technical:
- Installed ESLint with TypeScript support
- Fixed all lint errors (0 errors)
- Phase 1 files have zero warnings
- Used existing toast from sonner (not reinvented)
- Updated routes in App.tsx

📝 Files Created:
- Store.tsx (currency preview, address, timezone)
- Payments.tsx (provider cards, manual methods)
- Shipping.tsx (zone cards, rates, local pickup)
- SettingsLayout.tsx, SettingsCard.tsx, SettingsSection.tsx, ToggleField.tsx

Phase 1 complete: 18-24 hours estimated work

admin-spa/src/components/DummyDataToggle.tsx

@@ -15,13 +15,14 @@ export function DummyDataToggle() {
   const location = useLocation();
   const isDashboardRoute = location.pathname === '/' || location.pathname.startsWith('/dashboard');
 
-  // Use dashboard context for dashboard routes, otherwise use local state
-  const dashboardContext = isDashboardRoute ? useDashboardContext() : null;
+  // Always call hooks unconditionally
+  const dashboardContext = useDashboardContext();
   const localToggle = useDummyDataToggle();
 
-  const useDummyData = isDashboardRoute ? dashboardContext!.useDummyData : localToggle.useDummyData;
+  // Use dashboard context for dashboard routes, otherwise use local state
+  const useDummyData = isDashboardRoute ? dashboardContext.useDummyData : localToggle.useDummyData;
   const toggleDummyData = isDashboardRoute
-    ? () => dashboardContext!.setUseDummyData(!dashboardContext!.useDummyData)
+    ? () => dashboardContext.setUseDummyData(!dashboardContext.useDummyData)
     : localToggle.toggleDummyData;
 
   // Only show in development (always show for now until we have real data)

admin-spa/src/components/nav/DashboardSubmenuBar.tsx

@@ -30,9 +30,9 @@ export default function DashboardSubmenuBar({ items = [], fullscreen = false }:
   return (
     <div data-submenubar className={`border-b border-border bg-background md:bg-background/95 md:backdrop-blur md:supports-[backdrop-filter]:bg-background/60 sticky ${topClass} z-20`}>
       <div className="px-4 py-2">
-        <div className="flex items-center justify-between gap-4">
+        <div className="flex flex-col lg:flex-row items-center justify-between gap-4">
           {/* Submenu Links */}
-          <div className="flex gap-2 overflow-x-auto no-scrollbar">
+          <div className="flex gap-2 overflow-x-auto no-scrollbar w-full flex-shrink">
             {items.map((it) => {
               const key = `${it.label}-${it.path || it.href}`;
               const isActive = !!it.path && (
@@ -65,9 +65,9 @@ export default function DashboardSubmenuBar({ items = [], fullscreen = false }:
           </div>
 
           {/* Period Selector, Refresh & Dummy Toggle */}
-          <div className="flex items-center gap-2 flex-shrink-0">
+          <div className="flex justify-end lg:items-center gap-2 flex-shrink-0 w-full flex-shrink">
             <Select value={period} onValueChange={setPeriod}>
-              <SelectTrigger className="w-[140px] h-8">
+              <SelectTrigger className="w-full lg:w-[140px] h-8">
                 <SelectValue />
               </SelectTrigger>
               <SelectContent>

admin-spa/src/components/nav/SubmenuBar.tsx

@@ -5,11 +5,12 @@ import type { SubItem } from '@/nav/tree';
 type Props = { items?: SubItem[] };
 
 export default function SubmenuBar({ items = [] }: Props) {
+  // Always call hooks first
+  const { pathname } = useLocation();
+  
   // Single source of truth: props.items. No fallbacks, no demos, no path-based defaults
   if (items.length === 0) return null;
 
-  const { pathname } = useLocation();
-
   return (
     <div data-submenubar className="border-b border-border bg-background/95">
       <div className="px-4 py-2">