feat: Add event automation system for plugins attached to appointments

- Add GlobalEventPlugin model for auto-attaching plugins to all events
- Create signals for auto-attachment on new events and rescheduling
- Add API endpoints for global event plugins (CRUD, toggle, reapply)
- Update CreateTaskModal with "Scheduled Task" vs "Event Automation" choice
- Add option to apply to all events or future events only
- Display event automations in Tasks page alongside scheduled tasks
- Add EditEventAutomationModal for editing trigger and timing
- Handle event reschedule - update Celery task timing on time/duration changes
- Add Marketplace to Plugins menu in sidebar

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

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

frontend/src/pages/MyPlugins.tsx

@@ -18,7 +18,9 @@ import {
   Bot,
   Package as PackageIcon,
   X,
-  AlertTriangle
+  AlertTriangle,
+  Clock,
+  Settings
 } from 'lucide-react';
 import api from '../api/client';
 import { PluginInstallation, PluginCategory } from '../types';
@@ -377,6 +379,27 @@ const MyPlugins: React.FC = () => {
 
                   {/* Actions */}
                   <div className="flex items-center gap-2 ml-4">
+                    {/* Schedule button - only if not already scheduled */}
+                    {!plugin.scheduledTaskId && (
+                      <button
+                        onClick={(e) => {
+                          e.stopPropagation();
+                          navigate('/tasks');
+                        }}
+                        className="flex items-center gap-2 px-3 py-2 bg-blue-600 text-white rounded-lg hover:bg-blue-700 transition-colors text-sm font-medium"
+                        title={t('plugins.schedule', 'Schedule')}
+                      >
+                        <Clock className="h-4 w-4" />
+                        {t('plugins.schedule', 'Schedule')}
+                      </button>
+                    )}
+                    {/* Already scheduled indicator */}
+                    {plugin.scheduledTaskId && (
+                      <span className="flex items-center gap-1.5 px-3 py-2 bg-green-100 dark:bg-green-900/30 text-green-700 dark:text-green-300 rounded-lg text-sm font-medium">
+                        <Clock className="h-4 w-4" />
+                        {t('plugins.scheduled', 'Scheduled')}
+                      </span>
+                    )}
                     {plugin.hasUpdate && (
                       <button
                         onClick={(e) => {