feat: Add comprehensive sandbox mode, public API system, and platform support

This commit adds major features for sandbox isolation, public API access, and platform support ticketing.

## Sandbox Mode
- Add sandbox mode toggle for businesses to test features without affecting live data
- Implement schema-based isolation for tenant data (appointments, resources, services)
- Add is_sandbox field filtering for shared models (customers, staff, tickets)
- Create sandbox middleware to detect and set sandbox mode from cookies
- Add sandbox context and hooks for React frontend
- Display sandbox banner when in test mode
- Auto-reload page when switching between live/test modes
- Prevent platform support tickets from being created in sandbox mode

## Public API System
- Full REST API for external integrations with businesses
- API token management with sandbox/live token separation
- Test tokens (ss_test_*) show full plaintext for easy testing
- Live tokens (ss_live_*) are hashed and secure
- Security validation prevents live token plaintext storage
- Comprehensive test suite for token security
- Rate limiting and throttling per token
- Webhook support for real-time event notifications
- Scoped permissions system (read/write per resource type)
- API documentation page with interactive examples
- Token revocation with confirmation modal

## Platform Support
- Dedicated support page for businesses to contact SmoothSchedule
- View all platform support tickets in one place
- Create new support tickets with simplified interface
- Reply to existing tickets with conversation history
- Platform tickets have no admin controls (no priority/category/assignee/status)
- Internal notes hidden for platform tickets (business can't see them)
- Quick help section with links to guides and API docs
- Sandbox warning prevents ticket creation in test mode
- Business ticketing retains full admin controls (priority, assignment, internal notes)

## UI/UX Improvements
- Add notification dropdown with real-time updates
- Staff permissions UI for ticket access control
- Help dropdown in sidebar with Platform Guide, Ticketing Help, API Docs, and Support
- Update sidebar "Contact Support" to "Support" with message icon
- Fix navigation links to use React Router instead of anchor tags
- Remove unused language translations (Japanese, Portuguese, Chinese)

## Technical Details
- Sandbox middleware sets request.sandbox_mode from cookies
- ViewSets filter data by is_sandbox field
- API authentication via custom token auth class
- WebSocket support for real-time ticket updates
- Migration for sandbox fields on User, Tenant, and Ticket models
- Comprehensive documentation in SANDBOX_MODE_IMPLEMENTATION.md

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

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

frontend/src/pages/Settings.tsx

@@ -9,6 +9,7 @@ import { useCustomDomains, useAddCustomDomain, useDeleteCustomDomain, useVerifyC
 import { useBusinessOAuthCredentials, useUpdateBusinessOAuthCredentials } from '../hooks/useBusinessOAuthCredentials';
 import { useResourceTypes, useCreateResourceType, useUpdateResourceType, useDeleteResourceType } from '../hooks/useResourceTypes';
 import OnboardingWizard from '../components/OnboardingWizard';
+import ApiTokensSection from '../components/ApiTokensSection';
 
 // Curated color palettes with complementary primary and secondary colors
 const colorPalettes = [
@@ -98,7 +99,7 @@ const colorPalettes = [
   },
 ];
 
-type SettingsTab = 'general' | 'domains' | 'authentication' | 'resources';
+type SettingsTab = 'general' | 'domains' | 'authentication' | 'resources' | 'api-tokens';
 
 // Resource Types Management Section Component
 const ResourceTypesSection: React.FC = () => {
@@ -645,6 +646,7 @@ const SettingsPage: React.FC = () => {
     { id: 'resources' as const, label: 'Resource Types', icon: Layers },
     { id: 'domains' as const, label: 'Domains', icon: Globe },
     { id: 'authentication' as const, label: 'Authentication', icon: Lock },
+    { id: 'api-tokens' as const, label: 'API Tokens', icon: Key },
   ];
 
   return (
@@ -1853,6 +1855,11 @@ const SettingsPage: React.FC = () => {
         </div>
       )}
 
+      {/* API TOKENS TAB */}
+      {activeTab === 'api-tokens' && isOwner && (
+        <ApiTokensSection />
+      )}
+
       {/* Floating Action Buttons */}
       <div className="fixed bottom-0 left-64 right-0 p-4 bg-white dark:bg-gray-800 border-t border-gray-200 dark:border-gray-700 shadow-lg z-40 md:left-64">
         <div className="max-w-4xl mx-auto flex items-center justify-between">