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/contexts/SandboxContext.tsx

@@ -0,0 +1,66 @@
+/**
+ * Sandbox Context
+ * Provides sandbox mode state and toggle functionality throughout the app
+ */
+
+import React, { createContext, useContext, useEffect, ReactNode } from 'react';
+import { useSandboxStatus, useToggleSandbox } from '../hooks/useSandbox';
+
+interface SandboxContextType {
+  /** Whether the app is currently in sandbox/test mode */
+  isSandbox: boolean;
+  /** Whether sandbox mode is available for this business */
+  sandboxEnabled: boolean;
+  /** Whether the sandbox status is loading */
+  isLoading: boolean;
+  /** Toggle between live and sandbox mode */
+  toggleSandbox: (enableSandbox: boolean) => Promise<void>;
+  /** Whether a toggle operation is in progress */
+  isToggling: boolean;
+}
+
+const SandboxContext = createContext<SandboxContextType | undefined>(undefined);
+
+interface SandboxProviderProps {
+  children: ReactNode;
+}
+
+export const SandboxProvider: React.FC<SandboxProviderProps> = ({ children }) => {
+  const { data: status, isLoading } = useSandboxStatus();
+  const toggleMutation = useToggleSandbox();
+
+  const toggleSandbox = async (enableSandbox: boolean) => {
+    await toggleMutation.mutateAsync(enableSandbox);
+  };
+
+  // Store sandbox mode in localStorage for persistence across tabs
+  useEffect(() => {
+    if (status?.sandbox_mode !== undefined) {
+      localStorage.setItem('sandbox_mode', String(status.sandbox_mode));
+    }
+  }, [status?.sandbox_mode]);
+
+  const value: SandboxContextType = {
+    isSandbox: status?.sandbox_mode ?? false,
+    sandboxEnabled: status?.sandbox_enabled ?? false,
+    isLoading,
+    toggleSandbox,
+    isToggling: toggleMutation.isPending,
+  };
+
+  return (
+    <SandboxContext.Provider value={value}>
+      {children}
+    </SandboxContext.Provider>
+  );
+};
+
+export const useSandbox = (): SandboxContextType => {
+  const context = useContext(SandboxContext);
+  if (context === undefined) {
+    throw new Error('useSandbox must be used within a SandboxProvider');
+  }
+  return context;
+};
+
+export default SandboxContext;