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/routes/api/settings/+server.ts

@@ -50,7 +50,7 @@ export const PUT: RequestHandler = async ({ request, locals }) => {
 	}
 
 	// locale is optional — if provided it must be a known value
-	const validLocales = ['en', 'ru', 'id', 'pt-BR', 'fr'];
+	const validLocales = ['en', 'ru', 'id', 'pt', 'fr'];
 	if (body.locale !== undefined && !validLocales.includes(body.locale)) {
 		error(400, `Invalid locale — must be one of: ${validLocales.join(', ')}`);
 	}