"Invalid URL" TypeError from the UI as it talks to the API

[basilesimon]

Since we've moved to SvelteKit, the available fetch object is a little different... which requires an absolute URL, otherwise this error crops up:

(node:96340) UnhandledPromiseRejectionWarning: TypeError [ERR_INVALID_URL]: Invalid URL: /api/list-docs
    at onParseError (internal/url.js:279:9)
    at new URL (internal/url.js:355:5)

See ui/src/lib/Ledger/index.ts for the culprits:

const res = await fetch(`api/list-docs`);

This issue outlines that we need to move to this initial load()

[basilesimon]

Must reassess in light of this other PR