fix: sync in-memory publication URL after custom domain changes

[zzstoatzz]

problem

when a user sets up a custom domain via the CustomDomainModal, the URL is correctly written to ATProto (site.standard.publication record), but the in-memory data.publication.url is never updated. this causes a subtle bug:

1. user verifies custom domain → ATProto record gets url: "https://mycustomdomain.com"
2. user edits their site and saves → savePage() runs
3. savePage() checks if (!data.publication.url) — but the old blento.app/{handle} URL is still in memory, so this guard is truthy
4. the stale blento.app/{handle} URL gets written back to ATProto, overwriting the custom domain URL

the same issue exists in reverse when removing a custom domain — the URL field is stripped from ATProto but stays in memory.

impact

downstream consumers that index site.standard.publication records end up storing the wrong URL. for example, a document at https://marcobonomo.dev/blog/manifesto-cucina-amatoriale gets indexed with https://blento.app/marcobonomo.dev/blog/manifesto-cucina-amatoriale, which 404s.

found via https://pub-search.waow.tech/?q=%22in+una+libreria%22

fix

add an onUrlChange callback prop to CustomDomainModal. after verify() succeeds, it calls back with the new https://{domain} URL. after removeDomain() succeeds, it calls back with undefined. Account.svelte wires this up to update data.publication.url in place.

changes

• CustomDomainModal.svelte: add onUrlChange prop, call it after verify and remove
• Account.svelte: pass onUrlChange callback to sync data.publication.url

[zzstoatzz]

the LinkCardSettings.svelte changes are just prettier-plugin-tailwindcss reordering class names into canonical order to get CI green (lmk if im wrong and this wasn't preexisting)