feat: add CMS page routes

[glitchedmob]

Adds the SvelteKit CMS page layer so conference content can render through the migrated app.

• Loads conference home, generic content pages, speaker detail pages, and registration routes from server loaders.
• Renders CMS blocks with the existing Svelte components and fetches schedule, sponsor, and speaker-session data only when those views need it.
• Maps leaf metadata into the shared head owner and keeps success pages noindexed.
• Ports the OveIt iframe mount and hash-to-next handling without clearing the parent hash.