chore(landing): run dev server on Node instead of Bun runtime

Bun runtime + Next 16 Turbopack dev server intermittently trips a
JavaScriptCore allocator panic ('pas panic: deallocation did fail ...
Alloc bit not set') after a few requests. Dropping --bun keeps Bun as
the package manager but runs next dev on Node, which is stable.

Build + start keep --bun since one-shot invocations don't exhibit the
allocator drift.

Co-Authored-By: Claude Opus 4.7 (1M context) <[email protected]>

landing/package.json

@@ -3,7 +3,7 @@
   "version": "0.4.1",
   "description": "Landing page for voicebox.sh",
   "scripts": {
-    "dev": "bun --bun next dev --turbo",
+    "dev": "next dev --turbo",
     "build": "bun --bun next build",
     "start": "bun --bun next start",
     "lint": "next lint"