Add booking flow, business hours, and dark mode support

Features:
- Complete multi-step booking flow with service selection, date/time picker,
  auth (login/signup with email verification), payment, and confirmation
- Business hours settings page for defining when business is open
- TimeBlock purpose field (BUSINESS_HOURS, CLOSURE, UNAVAILABLE)
- Service resource assignment with prep/takedown time buffers
- Availability checking respects business hours and service buffers
- Customer registration via email verification code

UI/UX:
- Full dark mode support for all booking components
- Separate first/last name fields in signup form
- Back buttons on each wizard step
- Removed auto-redirect from confirmation page

API:
- Public endpoints for services, availability, business hours
- Customer verification and registration endpoints
- Tenant lookup from X-Business-Subdomain header

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontend/src/components/Sidebar.tsx

@@ -17,6 +17,7 @@ import {
   Plug,
   FileSignature,
   CalendarOff,
+  LayoutTemplate,
 } from 'lucide-react';
 import { Business, User } from '../types';
 import { useLogout } from '../hooks/useAuth';
@@ -119,6 +120,7 @@ const Sidebar: React.FC<SidebarProps> = ({ business, user, isCollapsed, toggleCo
               icon={CalendarDays}
               label={t('nav.scheduler')}
               isCollapsed={isCollapsed}
+              badgeElement={<UnfinishedBadge />}
             />
           )}
           {!isStaff && (
@@ -152,6 +154,13 @@ const Sidebar: React.FC<SidebarProps> = ({ business, user, isCollapsed, toggleCo
         {/* Manage Section - Staff+ */}
         {canViewManagementPages && (
           <SidebarSection title={t('nav.sections.manage', 'Manage')} isCollapsed={isCollapsed}>
+            <SidebarItem
+              to="/site-editor"
+              icon={LayoutTemplate}
+              label={t('nav.siteBuilder', 'Site Builder')}
+              isCollapsed={isCollapsed}
+              badgeElement={<UnfinishedBadge />}
+            />
             <SidebarItem
               to="/customers"
               icon={Users}