chore(dev): enable Turbopack and lift typedRoutes out of experimental

`pnpm dev` now runs `next dev --turbopack` (10–20× speedup vs webpack
on cold compile and HMR). Promote `typedRoutes` out of `experimental`
to match Next 15.5's stable surface; auto-update `next-env.d.ts` to
reference the generated routes.d.ts. Ignore that file in eslint since
Next regenerates it and the triple-slash style is fixed by the
framework.

`next.config.ts` has no custom `webpack()` hook so reverting to the
plain dev server is one line if needed.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

eslint.config.mjs

@@ -21,7 +21,7 @@ const eslintConfig = [
     },
   },
   {
-    ignores: ["client-portal/**"],
+    ignores: ["client-portal/**", "next-env.d.ts"],
   },
 ];