Add local dev seed data (devenv.sh seed)

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

CLAUDE.md

@@ -23,6 +23,7 @@ Without Docker (native stack: uvicorn `--reload` on :5000, Vite HMR on **:8020**
 ```bash
 src/dev/devenv.sh setup     # backend venv (src/backend/.venv), npm ci for frontend + e2e, Mailpit binary into src/.devenv/bin
 src/dev/devenv.sh start     # idempotent; waits until everything answers. Also: stop | restart | status | logs [service] | reset (wipes DB + uploads)
+src/dev/devenv.sh seed      # sample users (admin, alice, bob, carol @example.com), an open and a closed order; local only, idempotent
 cd src/frontend && npx tsc --noEmit                # type checking (vite build does not run tsc)
 ```