Server-render the public pages

SSR for the pages visitors actually hit: home, albums list, album detail, artists list, artist detail, stats.

• Route loaders fetch on the server during the first render, then on the client for navigation
• The RPC client needs an environment-aware base URL: the internal docker hostname server-side, the public origin in the browser
• Admin routes (create/edit forms, bookmarks, search, settings) stay client-rendered, so no auth cookies need forwarding during SSR
• Verify with JS disabled that the public pages render real content