Replace Miro?

Build me a personal whiteboard app to replace Miro. Requirements:

- Do not write a canvas engine from scratch: build on the tldraw SDK (React +
  Vite). It already does shapes, sticky notes, connectors, and selection well.
- A local web app on localhost:4900 with a board picker: named boards with
  thumbnails, create, rename, delete.
- Each board autosaves its tldraw snapshot JSON to SQLite (better-sqlite3 behind a
  small Express API) 2 seconds after the last change, keeping the previous 20
  snapshots as undo insurance.
- A toolbar button exports the current board as PNG and SVG to
  ~/Whiteboards/<board-name>.png.
- A template row on the new-board screen seeded from JSON files in templates/:
  retro grid, brainstorm columns, weekly plan.
- Works fully offline, binds to localhost, no accounts, no telemetry.
- Optional: share-with-one-person mode over my private network using tldraw's sync
  package, two cursors max. Skip it if it costs more than an hour.
- Out of scope: workshop facilitation tools (timers, voting), integrations, and
  performance tuning for 50-person boards. This is my thinking canvas, not a venue.
- README: dev and build commands, and where board data lives on disk.