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/profile/+page.server.ts

@@ -1,6 +1,6 @@
-import { fail, redirect } from '@sveltejs/kit';
-import type { Actions, PageServerLoad } from './$types';
-import { changePassword, listUserSessions, getUserByUsername } from '$lib/server/pocketbase';
+import { redirect } from '@sveltejs/kit';
+import type { PageServerLoad } from './$types';
+import { listUserSessions, getUserByUsername } from '$lib/server/pocketbase';
 import { resolveAvatarUrl } from '$lib/server/minio';
 import { log } from '$lib/server/logger';
 
@@ -38,40 +38,3 @@ export const load: PageServerLoad = async ({ locals }) => {
 		}))
 	};
 };
-
-export const actions: Actions = {
-	changePassword: async ({ request, locals }) => {
-		if (!locals.user) {
-			return fail(401, { error: 'Not logged in.' });
-		}
-
-		const data = await request.formData();
-		const current = (data.get('current') as string | null) ?? '';
-		const next = (data.get('next') as string | null) ?? '';
-		const confirm = (data.get('confirm') as string | null) ?? '';
-
-		if (!current || !next || !confirm) {
-			return fail(400, { error: 'All fields are required.' });
-		}
-		if (next.length < 8) {
-			return fail(400, { error: 'New password must be at least 8 characters.' });
-		}
-		if (next !== confirm) {
-			return fail(400, { error: 'New passwords do not match.' });
-		}
-
-		let ok: boolean;
-		try {
-			ok = await changePassword(locals.user.id, current, next);
-		} catch (e) {
-			log.error('profile', 'changePassword failed', { err: String(e) });
-			return fail(500, { error: 'An error occurred. Please try again.' });
-		}
-
-		if (!ok) {
-			return fail(401, { error: 'Current password is incorrect.' });
-		}
-
-		return { success: true };
-	}
-};