feat(ui): language persistence, theme fix, font/size settings, header quick-access

- Fix language not persisting after refresh: save locale in user_settings,
  set PARAGLIDE_LOCALE cookie from DB preference on server load
- Fix theme change not applying: context setter was mismatched (setTheme vs current)
- Add font family (system/serif/mono) and text size (sm/md/lg/xl) user settings
  stored in DB and applied via CSS custom properties
- Add theme color dots and language picker to desktop header for quick access
- Footer locale switcher now saves preference to DB before switching
- Remove change password section (OAuth-only, no password login)
- Fix active sessions piling up: reuse existing session on re-login via OAuth
- Extend speed step cycle to include 2.5× and 3.0× (matching profile slider)
- Replace plain checkbox with modern toggle switch for auto-next setting
- Fix catalogue status labels (ongoing/completed) to use translation keys
- Add font family and text size translation keys to all 5 locale files

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

ui/src/routes/+layout.server.ts

@@ -6,14 +6,14 @@ import { log } from '$lib/server/logger';
 // Routes that are accessible without being logged in
 const PUBLIC_ROUTES = new Set(['/login', '/disclaimer', '/privacy', '/dmca', '/terms']);
 
-export const load: LayoutServerLoad = async ({ locals, url }) => {
+export const load: LayoutServerLoad = async ({ locals, url, cookies }) => {
 	// Allow /auth/* (OAuth initiation + callbacks) without login
 	const isPublic = PUBLIC_ROUTES.has(url.pathname) || url.pathname.startsWith('/auth/');
 	if (!isPublic && !locals.user) {
 		redirect(302, `/login`);
 	}
 
-	let settings = { autoNext: false, voice: 'af_bella', speed: 1.0, theme: 'amber' };
+	let settings = { autoNext: false, voice: 'af_bella', speed: 1.0, theme: 'amber', locale: 'en', fontFamily: 'system', fontSize: 1.0 };
 	try {
 		const row = await getSettings(locals.sessionId, locals.user?.id);
 		if (row) {
@@ -21,13 +21,33 @@ export const load: LayoutServerLoad = async ({ locals, url }) => {
 				autoNext: row.auto_next ?? false,
 				voice: row.voice ?? 'af_bella',
 				speed: row.speed ?? 1.0,
-				theme: row.theme ?? 'amber'
+				theme: row.theme ?? 'amber',
+				locale: row.locale ?? 'en',
+				fontFamily: row.font_family ?? 'system',
+				fontSize: row.font_size ?? 1.0
 			};
 		}
 	} catch (e) {
 		log.warn('layout', 'failed to load settings', { err: String(e) });
 	}
 
+	// If user is logged in and has a non-English locale saved, ensure the
+	// PARAGLIDE_LOCALE cookie is set so the locale persists after refresh.
+	if (locals.user) {
+		const savedLocale = settings.locale ?? 'en';
+		if (savedLocale !== 'en') {
+			const currentCookieLocale = cookies.get('PARAGLIDE_LOCALE');
+			if (currentCookieLocale !== savedLocale) {
+				cookies.set('PARAGLIDE_LOCALE', savedLocale, {
+					path: '/',
+					maxAge: 34560000,
+					sameSite: 'lax',
+					httpOnly: false
+				});
+			}
+		}
+	}
+
 	return {
 		user: locals.user,
 		isPro: locals.isPro,