Improve the landing page: content and design

Follow-up to Add homepage — the landing page now exists at loomkeep.app, but it is a first pass. Both what it says and how it looks can go further.

Content

• No screenshots or visual proof of the app. Right now the hero shows an abstract placeholder panel instead of the real thing (library grid, a media detail page, the release calendar).
• Nothing about the mobile/PWA experience — that it installs to the home screen and sends push notifications is a selling point that is currently invisible.
• No answer to "why not Trakt / Simkl / TV Time?" — the multi-domain angle (video, games, books, music in one place) is stated but never contrasted.
• The self-hosting story is one short card. It deserves more: what the Docker stack actually gives you, which API keys are needed, the optional add-ons.
• No FAQ, no privacy/data-ownership section beyond a single bullet, no mention that the project is open source under an explicit license.
• Nothing about the roadmap or how to influence it (this board is not linked from the page).

Design

• The layout is a conventional stack of centered sections. The "Séance" identity (timecode metadata, letterbox rules, the amber marquee cartouche) is only lightly used — the page could look far more like a cinema programme and far less like a generic SaaS template.
• No motion or scroll-driven reveal, no depth. Everything lands flat.
• The hero placeholder panel is hidden entirely below the md breakpoint, so mobile visitors get text only.
• Section rhythm is uniform (same padding, same heading size) — nothing guides the eye toward the primary CTA.

Notes

Copy lives in apps/web/messages/{fr,en}.json under the landing_* prefix, so any rewrite has to land in both languages.