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/App.tsx

@@ -39,6 +39,7 @@ import Resources from './pages/Resources';
 import Services from './pages/Services';
 import Staff from './pages/Staff';
 import CustomerDashboard from './pages/customer/CustomerDashboard';
+import CustomerSupport from './pages/customer/CustomerSupport';
 import ResourceDashboard from './pages/resource/ResourceDashboard';
 import BookingPage from './pages/customer/BookingPage';
 import TrialExpired from './pages/TrialExpired';
@@ -47,7 +48,7 @@ import Upgrade from './pages/Upgrade';
 // Import platform pages
 import PlatformDashboard from './pages/platform/PlatformDashboard';
 import PlatformBusinesses from './pages/platform/PlatformBusinesses';
-import PlatformSupport from './pages/platform/PlatformSupport';
+import PlatformSupportPage from './pages/platform/PlatformSupport';
 import PlatformUsers from './pages/platform/PlatformUsers';
 import PlatformSettings from './pages/platform/PlatformSettings';
 import ProfileSettings from './pages/ProfileSettings';
@@ -56,6 +57,10 @@ import EmailVerificationRequired from './pages/EmailVerificationRequired';
 import AcceptInvitePage from './pages/AcceptInvitePage';
 import TenantOnboardPage from './pages/TenantOnboardPage';
 import Tickets from './pages/Tickets'; // Import Tickets page
+import HelpGuide from './pages/HelpGuide'; // Import Platform Guide page
+import HelpTicketing from './pages/HelpTicketing'; // Import Help page for ticketing
+import HelpApiDocs from './pages/HelpApiDocs'; // Import API documentation page
+import PlatformSupport from './pages/PlatformSupport'; // Import Platform Support page (for businesses to contact SmoothSchedule)
 import { Toaster } from 'react-hot-toast'; // Import Toaster for notifications
 
 const queryClient = new QueryClient({
@@ -321,7 +326,10 @@ const AppContent: React.FC = () => {
               <Route path="/platform/users" element={<PlatformUsers onMasquerade={handleMasquerade} />} />
             </>
           )}
-          <Route path="/platform/support" element={<PlatformSupport />} />
+          <Route path="/platform/support" element={<PlatformSupportPage />} />
+          <Route path="/help/guide" element={<HelpGuide />} />
+          <Route path="/help/ticketing" element={<HelpTicketing />} />
+          <Route path="/help/api" element={<HelpApiDocs />} />
           {user.role === 'superuser' && (
             <Route path="/platform/settings" element={<PlatformSettings />} />
           )}
@@ -346,19 +354,47 @@ const AppContent: React.FC = () => {
 
   // Customer users
   if (user.role === 'customer') {
+    // Wait for business data to load
+    if (businessLoading) {
+      return <LoadingScreen />;
+    }
+
+    // Handle business not found for customers
+    if (!business) {
+      return (
+        <div className="min-h-screen flex items-center justify-center bg-gray-50 dark:bg-gray-900">
+          <div className="text-center max-w-md p-6">
+            <h2 className="text-2xl font-bold text-red-600 dark:text-red-400 mb-4">Business Not Found</h2>
+            <p className="text-gray-600 dark:text-gray-400 mb-4">
+              Unable to load business data. Please try again.
+            </p>
+            <button
+              onClick={handleSignOut}
+              className="px-4 py-2 bg-gray-600 text-white rounded hover:bg-gray-700"
+            >
+              Sign Out
+            </button>
+          </div>
+        </div>
+      );
+    }
+
     return (
       <Routes>
         <Route
           element={
             <CustomerLayout
-              business={business || ({} as any)}
+              business={business}
               user={user}
+              darkMode={darkMode}
+              toggleTheme={toggleTheme}
             />
           }
         >
           <Route path="/" element={<CustomerDashboard />} />
           <Route path="/book" element={<BookingPage />} />
           <Route path="/payments" element={<Payments />} />
+          <Route path="/support" element={<CustomerSupport />} />
           <Route path="/profile" element={<ProfileSettings />} />
           <Route path="/verify-email" element={<VerifyEmail />} />
           <Route path="*" element={<Navigate to="/" />} />
@@ -470,6 +506,10 @@ const AppContent: React.FC = () => {
           />
           <Route path="/scheduler" element={<Scheduler />} />
           <Route path="/tickets" element={<Tickets />} />
+          <Route path="/help/guide" element={<HelpGuide />} />
+          <Route path="/help/ticketing" element={<HelpTicketing />} />
+          <Route path="/help/api" element={<HelpApiDocs />} />
+          <Route path="/support" element={<PlatformSupport />} />
           <Route
             path="/customers"
             element={