fix(e2e): fix locale cookie httpOnly and add hydration waits

Paraglide's client-side setLocale writes the locale via document.cookie,
which silently fails for HttpOnly cookies. SvelteKit's cookies.set()
defaults to httpOnly: true, so locale switching never worked in tests.
Fix by setting httpOnly: false on the locale cookie (it's a UI preference,
not a credential — no security concern).

Add waitForSelector('[data-hydrated]') before any click that relies on
SvelteKit JavaScript event handlers. Without this, the click fires before
hydration and the onclick handler is not yet registered.

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

frontend/src/hooks.server.ts

@@ -11,7 +11,7 @@ const handleLocaleDetection: Handle = ({ event, resolve }) => {
 	if (!event.cookies.get(cookieName)) {
 		const locale = detectLocale(event.request.headers.get('accept-language') ?? '');
 		if (locale) {
-			event.cookies.set(cookieName, locale, { path: '/', sameSite: 'lax', maxAge: cookieMaxAge });
+			event.cookies.set(cookieName, locale, { path: '/', sameSite: 'lax', maxAge: cookieMaxAge, httpOnly: false });
 		}
 	}
 	return resolve(event);