feat: archive scanned conversations locally

[Lefeaker]

Summary

Implement the local archive MVP for scanned AI conversations.

This adds the host-side pipeline that receives scan payloads from the recipe webview, stores them in local SQLite, rebuilds Markdown exports, supports manual rescan from the app menu, and includes cleanup/export tooling for archive maintenance.

What Changed

• add local archive storage under src/archive/
  • SQLite initialization
  • schema for accounts, conversations, messages
  • archive persistence service
• receive aihub-scan-messages in ServicesStore
• add recipe preload bridge support for rescan
• add menu action: Rescan Current Conversation
  • shortcut: CmdOrCtrl+Shift+Alt+S
• add export script
  • scripts/export-ai-hub-archive.cjs
• add cleanup script
  • scripts/cleanup-ai-hub-archive.cjs
• improve local metadata handling when local recipe files / sandbox config are missing
• fix archive naming and dedupe behavior
  • use canonical conversation key from /c/<id> when available
  • prevent title-only duplicates
  • dedupe exports per account + conversation key
  • safely clean historical duplicate conversation rows from SQLite

Why

This is the minimum viable local archive chain:

1. scan current open conversation
2. send structured messages to host
3. persist to local SQLite
4. export Markdown from persisted records

Validation

• targeted lint / typecheck / tests passed through commit hooks
• archive export succeeded
• verified Markdown output under ~/Library/Application Support/FerdiumDev/ai-hub/conversations/
• verified second-account conversations can be archived independently
• verified duplicate historical conversation rows were backed up, cleaned, and re-exported

Output Paths

• SQLite: ~/Library/Application Support/FerdiumDev/ai-hub/archive.db
• latest Markdown: ~/Library/Application Support/FerdiumDev/ai-hub/conversation.md
• per-conversation Markdown: ~/Library/Application Support/FerdiumDev/ai-hub/conversations/

Scope Notes

• supports current open conversation full scan
• does not yet do incremental live sync while chatting
• does not yet wire Gemini / Claude archive pipelines
• does not yet handle attachments, references, summaries, or memory features