Shim make dev and make build, format backend/ markdown (closes #28)

make dev ran yarn dev inline and there was no make build. Both are now
shims, over script/dev and the new script/build. .prettierignore stops
leaving out backend/, so backend/README.md is formatted and checked;
backend/.golangci.yml is left out by name instead: it is the org
standard file whose sha256 backend/script/lint checks, and prettier
would reindent it. .claude/ stays in .prettierignore, as git does not
ignore it. script/install-precommit and the date on bootstrap's pins go
back to the org model; bootstrap, fmt and fmt-check keep what the Go
backend and eslint need, each with a comment saying so.

Model: opus-5-5

script/dev

@@ -0,0 +1,13 @@
+#!/bin/sh
+# script/dev: run the frontend's Vite dev server. It proxies /api to a
+# netwatch-server running locally (see vite.config.js).
+set -eu
+
+ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
+
+main() {
+    cd "$ROOT"
+    yarn dev
+}
+
+main "$@"