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.

site/layouts/partials/store-badges.html

@@ -0,0 +1,12 @@
+{{- /* Renders store links only when configured, so nothing broken shows pre-launch. */ -}}
+<div class="store-badges">
+  {{- with .Site.Params.playStoreURL -}}
+  <a class="badge" href="{{ . }}">Google Play</a>
+  {{- end -}}
+  {{- with .Site.Params.fdroidURL -}}
+  <a class="badge" href="{{ . }}">F-Droid</a>
+  {{- end -}}
+  {{- if and (not .Site.Params.playStoreURL) (not .Site.Params.fdroidURL) -}}
+  <p class="coming-soon">{{ T "getItComingSoon" }}</p>
+  {{- end -}}
+</div>