feat: member portal Sprint 9 — Ask AI (RAG over message archive)

- AskAIQuery model + migration (logs question/answer/citations per member)
- AskAIService: RAG pipeline — retrieve via tenant-isolated SearchService (Meili),
  ground LLM in top-8 snippets with inline [n] citations, degrade gracefully when
  OPENROUTER_API_KEY absent or no context (snippet fallback)
- Shared api/common/llm-client.ts (mirrors worker's OpenRouter client)
- SearchModule now exports SearchService
- Member endpoints: GET/POST /my/ask (history + ask)
- /my/ask page + AskChat client component: question box, answer cards with sources
- Ask AI nav item (top of member nav)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

apps/web/app/my/layout.tsx

@@ -4,6 +4,7 @@ import { redirect } from 'next/navigation';
 
 const NAV = [
   { href: '/my', label: 'Dashboard' },
+  { href: '/my/ask', label: 'Ask AI' },
   { href: '/my/digest', label: 'Digest' },
   { href: '/my/events', label: 'Events' },
   { href: '/my/seva', label: 'Seva & Points' },