feat(web): tane.comunes.org landing + localized app screenshots

- Hugo site (site/): EN/ES intro + legal (generated from docs/legal), an
  ES/EN About page from docs/{que-es-tane,what-is-tane}.md, seed-green theme,
  responsive header, store-badge placeholders, multi-stage Hugo->nginx image.
- Golden screenshot harness (test/screenshots/): en,es,fr,de,pt,ja + RTL demo,
  real fonts via DejaVu Sans + FontManifest; skip-by-default tag so CI stays
  green. collect_screenshots.sh feeds site/ and fastlane phoneScreenshots.
- Drop editorial notes from the public explainer.

docs/what-is-tane.md

@@ -0,0 +1,72 @@
+# Tane — what it is
+
+**Tane** (種) means "seed" in Japanese; the full name, *tanemaki* (種まき), means "to sow / scatter seeds".
+
+## In one sentence
+
+A simple, free app to **keep your seeds and share them** with whoever you like. It works
+**without internet** and with no company in the middle.
+
+## Why it's needed
+
+Today a handful of companies control much of the world's seed. Many seeds are made so they
+won't serve again: they give one harvest, but their seeds don't germinate well, so you have
+to **buy them again every year**. Meanwhile the traditional varieties — grown and improved
+over thousands of years — are being lost, and with them the knowledge of how to grow them.
+
+Sharing seeds is one of the oldest and most natural things there is, yet in some places it
+has become complicated or even fined (in France an association was penalised for handing out
+varieties that weren't on the official approved list). And the people who care for seeds
+still do it with notebooks and spreadsheets.
+
+## What it does, made easy
+
+- **Keep** — your seed inventory: what you have, from which year, how much, where it came
+  from, under **the name you use** (no Latin required). The same whether you have four
+  packets in a drawer or a group with hundreds of varieties.
+- **Share** — you say what you offer; someone nearby sees it and writes to you, to **give
+  away, swap or sell** if you want. You close the deal yourself, directly. No company steps
+  in or takes a commission.
+
+## Why it's different
+
+- **It's free and belongs to everyone.** It isn't owned by any company: anyone can use,
+  copy, translate or improve it, free and forever. It's more a *recipe that gets shared*
+  than a closed product — this is called **free software**. And whoever improves it is
+  bound to share those improvements just as freely, so no one can "close" it later (that's
+  **copyleft**).
+- **It works offline.** The basics run even out in the field with no signal.
+- **Your data is yours.** Your information is kept on **your own phone**, protected with a
+  key, not on some company's computers. We don't sell it or upload it anywhere. No ads.
+- **No one can shut it down or control it.** There's no central computer that everything
+  passes through: people communicate **directly with each other**, like passing seeds from
+  hand to hand. So no one can censor it or charge you to use it (that's what being
+  **decentralized** means).
+- **You trust by word of mouth.** You deal with people you know and with those vouched for
+  by people you trust — the way it's always worked in a village or at a fair — without
+  having to give your real name or phone number unless you want to.
+- **In many languages.** For anywhere in the world, not for a single country. Volunteers
+  translate it.
+
+## Who it's for
+
+Seed groups and networks, gardens and collectives, growers… and anyone with a few packets
+put away. For all ages, from 10 to 80.
+
+## The name
+
+**Tane** means "seed" (種). It comes from *tanemaki* (種まき), "to sow seeds" in Japanese, a
+nod to old customs of mutual aid between neighbours (sharing the work, saving together).
+
+## Where it stands and how to help
+
+In its early days. You can help by trying it out in a real seed group, translating it,
+sharing what you know about the varieties, or coding. It has no price and never will: it's
+sustained by volunteers, by the communities themselves, and by public funding for projects
+of common interest.
+
+---
+
+> *The idea underneath: traditional seeds are a heritage of humankind — everyone's and no
+> one's. Against those who would privatise them, Tane aims to make it easy for you to keep
+> them, multiply them and keep them moving.*