Ran the installed ocdsgen, and added a script that installs the dev tools

go generate ran ocdsgen with go run, from go.mod, but go-ocds had been
dropped from go.mod (nothing imports it, so go mod tidy removes it), which
broke go generate and so scripts/build.sh. It now runs the installed
ocdsgen from PATH, as it does swag.

scripts/install-dev-tools.sh installs the Go tools (ocdsgen v1.0.0 and swag
v2.0.0-rc6 pinned, as other versions could generate different code;
golangci-lint, goose and cobra-cli at their latest), checks for Node.js 24
or later and runs npm ci in web/. The README's dev tools section now points
to it and lists what each tool is for.

internal/findatender/ocds/generate.go

@@ -2,4 +2,4 @@
 // the EU profile, UK extension, and the other extensions in extensions.json.
 package ocds
 
-//go:generate go run git.avsdev.uk/Go/go-ocds/cmd/ocdsgen generate -c extensions.json -o ocds_gen.go -p ocds
+//go:generate ocdsgen generate -c extensions.json -o ocds_gen.go -p ocds