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/pages/MyPlugins.tsx

@@ -24,6 +24,7 @@ import {
 } from 'lucide-react';
 import api from '../api/client';
 import { PluginInstallation, PluginCategory } from '../types';
+import EmailTemplateSelector from '../components/EmailTemplateSelector';
 
 // Category icon mapping
 const categoryIcons: Record<PluginCategory, React.ReactNode> = {
@@ -689,7 +690,13 @@ const MyPlugins: React.FC = () => {
                         {variable.required && <span className="text-red-500 ml-1">*</span>}
                       </label>
 
-                      {variable.type === 'textarea' ? (
+                      {variable.type === 'email_template' ? (
+                        <EmailTemplateSelector
+                          value={configValues[key] || variable.default}
+                          onChange={(templateId) => setConfigValues({ ...configValues, [key]: templateId })}
+                          required={variable.required}
+                        />
+                      ) : variable.type === 'textarea' ? (
                         <textarea
                           value={configValues[key] !== undefined ? configValues[key] : (variable.default ? unescapeString(variable.default) : '')}
                           onChange={(e) => setConfigValues({ ...configValues, [key]: e.target.value })}