fix(setup): run npm commands from repo root after workspace promotion (#131)

Closes #130

## Summary

- `bootstrap()` and `deploy()` in `setup.sh` were both `cd`-ing into
`app/` and calling `npm run build:lambdas`, left over from before PR #53
promoted the npm workspace root from `app/` to the repo root
- Changed `cd "$SCRIPT_DIR/app"` → `cd "$SCRIPT_DIR"` in both functions
so `npm ci` runs from the workspace root and correctly hoists all
dependencies
- Changed `npm run build:lambdas` → `npm run app:build:lambdas` to match
the root-level script alias
- Fixed the stale "next steps" dev command in the bootstrap output (`cd
app && npm run dev` → `npm run app:dev`)
- Removed `app/package-lock.json` — orphaned lockfile from before the
workspace root promotion that could confuse npm

## Test plan

- [ ] Run `./setup.sh` on a clean clone — confirm `npm ci` succeeds at
the repo root and Lambda bundles build without TS2307 errors
- [ ] Run `./setup.sh deploy` — confirm `npm run app:build:lambdas` runs
successfully from the repo root
- [ ] Confirm `app/package-lock.json` is gone and `npm ci` at repo root
still resolves all workspace deps correctly

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: CoderCoco