fix: disable SSR for authenticated app pages

WaveSurfer.js accesses window/AudioContext at module load time,
causing SSR to throw undefined on hard reload of track pages.
All (app) routes are auth-gated and fetch data client-side — SSR
provides no benefit here.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

apps/web/src/routes/(app)/+layout.ts

@@ -0,0 +1 @@
+export const ssr = false;