refactor: move studio to frontends workspace

- Move studio from root to frontends/studio/
- Add owner-tools frontend for live blog admin UI
- Add shared ui component library
- Set up npm workspaces for frontends
- Add enhanced code block extension for editor

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

frontends/studio/embed_testing.go

@@ -0,0 +1,18 @@
+//go:build testing
+
+package studio
+
+import (
+	"io/fs"
+	"net/http"
+)
+
+var distFS fs.FS
+
+func Handler() http.Handler {
+	return http.NotFoundHandler()
+}
+
+func Read(name string) ([]byte, error) {
+	return nil, fs.ErrNotExist
+}