feat: comprehensive frontend polish - UI/UX improvements across all pages

Public Pages:
- Landing page with server/client split and metadata export
- Cart page with ARIA accessibility and loading states
- Checkout page with form accessibility and proper design system
- Contact page with SEO metadata and improved accessibility
- Pricing page with enhanced FAQ accessibility
- Login page with Suspense boundaries and secure patterns

Brand Storefronts:
- Premium loading skeletons for Tuxedo and Indian River Direct
- Branded error boundaries with animations
- Loading.tsx for about, contact, FAQ, stops pages
- Error.tsx for all storefront subpages

Admin Dashboard:
- AdminSidebar: ARIA labels, keyboard navigation, mobile improvements
- DashboardClient: Stats cards, quick actions, usage progress
- Admin layout: Toast provider integration

Admin Orders/Products/Stops:
- Toast notification system with auto-dismiss
- Skeleton loading components (Table, Card, Stats, Form)
- Bulk actions (mark picked up, publish stops)
- Form validation with error styling

Admin Communications:
- AnalyticsDashboard: sparklines, stat cards, engagement badges
- CampaignComposerPage: step wizard, template selection, email preview
- SegmentBuilderPage: empty state, active segment handling
- ContactListPanel: loading skeletons, professional empty states
- MessageLogPanel: stats cards, engagement indicators
- HarvestReachNav: branded tab navigation
- All pages: metadata exports and loading.tsx

Admin Settings:
- SquareSyncSettingsClient: design system colors, save/cancel UX
- ShippingSettingsForm: validation, dirty state tracking
- Integrations page: proper layout with AI and communications sections
- Billing: improved plan comparison, add-on cards
- PaymentSettings: toggle components, validation

Wholesale Portal:
- Portal: loading skeletons, quantity stepper, search/filter
- Login/Register: FormField validation, success states
- Success/Cancel pages: animated checkmarks
- Employee portal: skeletons, empty states, mobile responsive

Water Log:
- FieldClient: loading step, progress indicator, spinner
- AdminClient: loading skeletons
- Admin pages: loading.tsx files

New Components:
- Toast.tsx/ToastContainer.tsx: comprehensive notification system
- Skeleton.tsx: shimmer loading components
- AdminToggle.tsx: consistent toggle/switch
- CommunicationsLoading.tsx: loading skeleton for comms
- ToastExport.ts: exports

CSS Improvements:
- Shimmer animation keyframes
- Toast slide-in animation

Accessibility:
- ARIA labels throughout
- Keyboard navigation
- Focus states
- Semantic HTML
- Screen reader support

src/styles/admin-design-system.css

@@ -327,4 +327,43 @@
   background-color: var(--admin-accent-light);
   color: var(--admin-accent-text);
   border: 1px solid var(--admin-accent);
+}
+
+/* === Shimmer Animation === */
+@keyframes shimmer {
+  0% {
+    background-position: 200% 0;
+  }
+  100% {
+    background-position: -200% 0;
+  }
+}
+
+.shimmer {
+  animation: shimmer 1.5s ease-in-out infinite;
+}
+
+/* === Toast Animations === */
+@keyframes slide-in-from-right {
+  from {
+    transform: translateX(100%);
+    opacity: 0;
+  }
+  to {
+    transform: translateX(0);
+    opacity: 1;
+  }
+}
+
+@keyframes fade-in {
+  from {
+    opacity: 0;
+  }
+  to {
+    opacity: 1;
+  }
+}
+
+.animate-in {
+  animation: slide-in-from-right 0.3s ease-out, fade-in 0.3s ease-out;
 }