- Add data-sveltekit-reload to the /login links so the browser performs a full
navigation (the client router intercepted them and aborted on the external
Zitadel redirect)
- Default post-login returnTo to / (home) since /explore is not built yet
- 'Empezar gratis' now starts the register flow (/login?mode=register)
New SvelteKit app in frontend/ (minimal template, TypeScript, TailwindCSS v4).
Adds the app shell (dark music theme navbar + footer) and a landing page with
hero and feature cards. CTAs point to /login and /explore (built in later parts).
Verified: production build succeeds and the page renders with Tailwind styles
applied (checked via preview).