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/layouts/SettingsLayout.tsx

@@ -21,6 +21,7 @@ import {
   CreditCard,
   AlertTriangle,
   Calendar,
+  Clock,
 } from 'lucide-react';
 import {
   SettingsSidebarSection,
@@ -109,6 +110,12 @@ const SettingsLayout: React.FC = () => {
               label={t('settings.booking.title', 'Booking')}
               description={t('settings.booking.description', 'Booking URL, redirects')}
             />
+            <SettingsSidebarItem
+              to="/settings/business-hours"
+              icon={Clock}
+              label={t('settings.businessHours.title', 'Business Hours')}
+              description={t('settings.businessHours.description', 'Operating hours')}
+            />
           </SettingsSidebarSection>
 
           {/* Branding Section */}