fix(auth): stop stale session cookies signing users out on refresh

@supabase/ssr 0.1.0 never removed the old unchunked session cookie once a
refreshed session grew past one cookie, and always read that stale copy
first. Every load then retried an already-used refresh token, which the
hosted auth server rejects, signing the user out.

Upgrade @supabase/ssr to 0.12 (and supabase-js to match) and move to the
getAll/setAll cookie API, which clears stale chunks when writing.

src/routes/+layout.server.ts

@@ -1,10 +1,12 @@
 import type { LayoutServerLoad } from './$types';
 
-export const load: LayoutServerLoad = async ({ locals: { safeGetSession } }) => {
+export const load: LayoutServerLoad = async ({ locals: { safeGetSession }, cookies }) => {
 	const { session, user } = await safeGetSession();
 
 	return {
 		session,
-		user
+		user,
+		// The universal layout load rebuilds a server-side client from these during SSR.
+		cookies: cookies.getAll()
 	};
 };