Consolidate white_label to remove_branding and add embed widget

- Rename white_label feature to remove_branding across frontend/backend
- Update billing catalog, plan features, and permission checks
- Add dark mode support to Recharts tooltips with useDarkMode hook
- Create embeddable booking widget with EmbedBooking page
- Add EmbedWidgetSettings for generating embed code
- Fix Appearance settings page permission check
- Update test files for new feature naming
- Add notes field to User model

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

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

frontend/src/hooks/usePlanFeatures.ts

@@ -81,7 +81,7 @@ export const FEATURE_NAMES: Record<FeatureKey, string> = {
   webhooks: 'Webhooks',
   api_access: 'API Access',
   custom_domain: 'Custom Domain',
-  white_label: 'White Label',
+  remove_branding: 'Remove Branding',
   custom_oauth: 'Custom OAuth',
   automations: 'Automations',
   can_create_automations: 'Custom Automation Creation',
@@ -104,7 +104,7 @@ export const FEATURE_DESCRIPTIONS: Record<FeatureKey, string> = {
   webhooks: 'Integrate with external services using webhooks',
   api_access: 'Access the SmoothSchedule API for custom integrations',
   custom_domain: 'Use your own custom domain for your booking site',
-  white_label: 'Remove SmoothSchedule branding and use your own',
+  remove_branding: 'Remove SmoothSchedule branding from customer-facing pages',
   custom_oauth: 'Configure your own OAuth credentials for social login',
   automations: 'Automate repetitive tasks with custom workflows',
   can_create_automations: 'Create custom automations tailored to your business needs',