feat: add Go release cache daemon (webicached) and HTTP API server (webid)

Rewrites the Node.js release classification pipeline in Go. webicached
fetches upstream releases, classifies assets, and writes legacy-format
JSON caches. webid serves the HTTP API (releases, resolve, bootstrap
scripts). Git-clone packages emit git_tag and git_commit_hash from
real repo clones — no fabricated refs.

internal/releases/node/node.go

@@ -0,0 +1,39 @@
+// Package node fetches Node.js releases from both official and unofficial
+// build sources.
+//
+// Official builds cover the standard platforms (linux-x64, osx-arm64, win-x64,
+// etc.). Unofficial builds add musl, loong64, and other targets that the
+// official CI doesn't produce.
+//
+// Both sources use the same index format, served by [nodedist].
+package nodedist
+
+import (
+	"context"
+	"iter"
+	"net/http"
+
+	"github.com/webinstall/webi-installers/internal/releases/nodedist"
+)
+
+const (
+	officialURL   = "https://nodejs.org/download/release"
+	unofficialURL = "https://unofficial-builds.nodejs.org/download/release"
+)
+
+// Fetch retrieves Node.js releases from both official and unofficial sources.
+// Yields one batch per source (official first, then unofficial).
+func Fetch(ctx context.Context, client *http.Client) iter.Seq2[[]nodedist.Entry, error] {
+	return func(yield func([]nodedist.Entry, error) bool) {
+		for entries, err := range nodedist.Fetch(ctx, client, officialURL) {
+			if !yield(entries, err) {
+				return
+			}
+		}
+		for entries, err := range nodedist.Fetch(ctx, client, unofficialURL) {
+			if !yield(entries, err) {
+				return
+			}
+		}
+	}
+}