feat: wire remaining PostHog events across all key user actions (#111)

- export_generated: session copy, copy-for-ticket, download
- ai_feature_used: copilot, assistant chat, session-to-flow, KB accelerator, flow assist
- psa_connected: ConnectWise integration creation
- session_shared: share link creation
- flow_created: troubleshooting editor, procedural editor, session-to-flow

All 9 events from the product analytics plan are now fully wired.

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/src/pages/AssistantChatPage.tsx

@@ -3,6 +3,7 @@ import { useLocation, useNavigate } from 'react-router-dom'
 import { Sparkles, Send, Loader2, Flag } from 'lucide-react'
 import { PageMeta } from '@/components/common/PageMeta'
 import { assistantChatApi } from '@/api/assistantChat'
+import { analytics } from '@/lib/analytics'
 import { toast } from '@/lib/toast'
 import { ChatSidebar } from '@/components/assistant/ChatSidebar'
 import { ChatMessage } from '@/components/assistant/ChatMessage'
@@ -147,6 +148,7 @@ export default function AssistantChatPage() {
 
     try {
       const response = await assistantChatApi.sendMessage(activeChatId, userMessage)
+      analytics.aiFeatureUsed({ feature: 'assistant_chat' })
       setMessages(prev => [
         ...prev,
         { role: 'assistant', content: response.content, suggestedFlows: response.suggested_flows },