[gnacho]

Follow-up to #224 and #227.

Problem

Below 861 px the install section still showed a sudo pacman -U command, a copy button and requirement cards about GNOME, nextcloudcmd and cargo build. A phone visitor cannot act on any of it, and the hero stopped offering the install CTA in #227, so the page led them to dead weight.

Changes

• landing/index.html: the desktop heading and lead get an install-desk class, and a mobile-only block states the real scope: NextSync is a Linux desktop application designed for GNOME, with no Android or iOS version.
• landing/styles.css: the mobile block is hidden by default, and below 861 px it replaces the install card and the requirement cards.
• landing/i18n.js: install.mTitle and install.mBody in ES and EN. Cache-bust to ?v=7.

Desktop content stays in the DOM, only hidden at that width, so SEO and desktop behaviour do not change. No other app is mentioned or recommended.

Verification

Playwright suite at 360, 390, 414, 1280 and 1440 px: 62/62 checks passing locally and 62/62 against production.

• Phones: install card, command, copy button, requirement cards and desktop heading hidden; the note visible, translated and free of any other app name.
• Desktop: install card, command, copy button, requirements and desktop heading as before, mobile note not rendered.
• No horizontal overflow, no console errors.

Already deployed to https://nextsync.cloudless.club/ and verified there.

Closes #231