fix(i18n+settings): rename pt-BR→pt, fix theme/locale persistence

Root cause: user_settings table was missing theme, locale, font_family,
font_size columns — PocketBase silently dropped them on every save.
Added the four columns via PocketBase API.

Also:
- listOne now sorts by -updated so the most-recent settings record wins
- PARAGLIDE_LOCALE cookie is now cleared when switching back to English
- pt-BR renamed to pt throughout (messages, inlang settings, validLocales)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

ui/src/lib/server/pocketbase.ts

@@ -197,8 +197,8 @@ async function countCollection(collection: string, filter = ''): Promise<number>
 	return (data as { totalItems: number }).totalItems ?? 0;
 }
 
-async function listOne<T>(collection: string, filter: string): Promise<T | null> {
-	const params = new URLSearchParams({ perPage: '1', filter });
+async function listOne<T>(collection: string, filter: string, sort = '-updated'): Promise<T | null> {
+	const params = new URLSearchParams({ perPage: '1', filter, sort });
 	const data = await pbGet<PBList<T>>(
 		`/api/collections/${collection}/records?${params.toString()}`
 	);