Resolve manifest via the mystic reference only

Drop the hardcoded MANIFEST_TX_ID fallback from the app, the deploy script
and the metadata prerender. The mystic reference now points at the manifest
that includes arweave-for-ao, so the UI picks up new ships without a code
change.

src/config.ts

@@ -5,7 +5,6 @@ export const BLOG_DEFAULT_DESCRIPTION =
   "A blog about cyberspace decentralization";
 export const BLOG_TWITTER_HANDLE = "";
 export const MANIFEST_REFERENCE_NAME = "mystic";
-export const MANIFEST_TX_ID = "SShELKFa2EsiB-OJbeoNOjAIxgah9OmRhxYXBF_M9wA";
 export const ARWEAVE_GATEWAY = "https://arweave.net";
 
 export const AO_URL = "https://push-1.forward.computer";