perf: faster dev startup and lighter bundle

- Switch dev default to Turbopack (5-14x faster compile); keep webpack as dev:webpack
- Tailwind v4 source() base so JIT scans identically under both bundlers
- Lazy-load @xyflow/react via next/dynamic to keep it out of the shared bundle
- optimizePackageImports for heavy barrel imports (xyflow, dnd-kit, material-symbols, marked)
- Replace blind setTimeout waits with TCP health-check (waitServerReady)
- Run checkForUpdate in parallel instead of blocking server spawn
- Background MITM/tunnel/cloudflared kills off the critical path

Co-authored-by: Cursor <cursoragent@cursor.com>

next.config.mjs

@@ -30,6 +30,8 @@ const nextConfig = {
     proxyClientMaxBodySize,
     // Cache fetch responses across HMR refreshes for faster dev reloads.
     serverComponentsHmrCache: true,
+    // Tree-shake heavy barrel imports to cut compile + bundle size
+    optimizePackageImports: ["@xyflow/react", "@dnd-kit/core", "@dnd-kit/sortable", "material-symbols", "marked"],
   },
   webpack: (config, { isServer }) => {
     // Ignore fs/path modules in browser bundle