xftp-web: fixes and multi-server upload

[shumvgolove]

xftp-web fixes

fix: await sodium.ready in crypto/keys.ts (+ digest.ts StateAddress cast) (c89ce1fb)
Add await sodium.ready in crypto/keys.ts. Cast crypto_hash_sha512_init() return to StateAddress in digest.ts.

multi-server parallel upload, remove pickRandomServer (21e32924)
Change uploadFile to accept servers[] instead of single server. Chunks randomly assigned to servers, uploaded in parallel. Remove pickRandomServer from web/servers.ts.

fix worker message race: wait for ready signal before posting messages (f408a701)
Fix production build hang: Vite adds top-level await import(...) in worker bundle, delaying self.onmessage assignment. Worker now posts {type: 'ready'} after init; backend awaits it before sending.

suppress vite build warnings: emptyOutDir, externals, chunkSizeWarningLimit (4956d143)
Add emptyOutDir: true, explicit external: ['node:http2', 'url'] for main and worker builds, raise chunkSizeWarningLimit to 1200 for libsodium WASM.

fix Haskell web tests: use agent+server API, wrap server in array, suppress debug logs (38ef4e9b)
Update XFTPWebTests.hs to use newXFTPAgent/closeXFTPAgent and (agent, server) signatures. Wrap single server in array for uploadFile. Redirect console.log to /dev/null in callNode.

remove dead APIs: un-export connectXFTP, delete closeXFTP (0db74db1)
Make connectXFTP private (used internally by agent). Remove unused closeXFTP.