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/hooks/useEditorAI.ts

@@ -1,5 +1,6 @@
 import { useState, useCallback, useRef } from 'react'
 import { editorAIApi } from '@/api/editorAI'
+import { analytics } from '@/lib/analytics'
 import type {
   AIActionType,
   EditorAIChatMessage,
@@ -101,6 +102,7 @@ export function useEditorAI({ flowType, treeId, getFlowContext, onFlowUpdate }:
         focalNodeId: currentFocalNodeId,
         flowContext: getFlowContext?.() || null,
       })
+      analytics.aiFeatureUsed({ feature: 'flow_assist' })
 
       setMessages((prev) => [
         ...prev,