feat: Add SMTP settings and collapsible email configuration UI

- Add SMTP fields to TicketEmailSettings model (host, port, TLS/SSL, credentials, from email/name)
- Update serializers with SMTP fields and is_smtp_configured flag
- Add TicketEmailTestSmtpView for testing SMTP connections
- Update frontend API types and hooks for SMTP settings
- Add collapsible IMAP and SMTP configuration sections with "Configured" badges
- Fix TypeScript errors in mockData.ts (missing required fields, type mismatches)

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

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

frontend/src/contexts/SandboxContext.tsx

@@ -58,7 +58,15 @@ export const SandboxProvider: React.FC<SandboxProviderProps> = ({ children }) =>
 export const useSandbox = (): SandboxContextType => {
   const context = useContext(SandboxContext);
   if (context === undefined) {
-    throw new Error('useSandbox must be used within a SandboxProvider');
+    // Return default values when used outside SandboxProvider
+    // This happens for platform admins who don't have sandbox mode
+    return {
+      isSandbox: false,
+      sandboxEnabled: false,
+      isLoading: false,
+      toggleSandbox: async () => {},
+      isToggling: false,
+    };
   }
   return context;
 };