feat(site): human-language 'what you can do' features section

Add a features section to the landing home (EN/ES) that describes what
Tane does by intent, not mechanism: inventory, care & calendar, labels &
backup, and the neighbourly sharing layer (offers, chat, trust, plantaré,
sync). Follows the existing pillars/values pattern (front-matter data +
template + CSS, RTL-safe). Reframe the beta status copy so the sharing
layer reads as 'arriving, in beta' rather than 'being built'.

site/content/_index.en.md

@@ -20,6 +20,37 @@ pillars:
   - icon: "🤝"
     title: "Share, as it's always been done"
     body: "Mark what you have spare to give away, swap or sell. Someone nearby finds it and contacts you — no middleman. Print a catalog of what you share to take to a seed fair."
+features:
+  title: "What you can do with Tane"
+  intro: "One quiet app for the whole life of a seed — keeping it, caring for it, and passing it on."
+  groups:
+    - icon: "🌱"
+      title: "Your seed bank, in your pocket"
+      items:
+        - "Add a seed in seconds — a photo and a name is all you need."
+        - "Track each batch by year and amount, in real units: cobs, pods, a handful, a jar."
+        - "Keep photos, notes and germination tests for every variety."
+        - "Give a seed several names, in several languages."
+    - icon: "🗓️"
+      title: "Care and timing"
+      items:
+        - "Seed-saving guidance for each crop: pollination, isolation, how many plants, drying."
+        - "A this-month calendar: what to sow, transplant or harvest for seed."
+        - "Friendly warnings when a seed is getting old, so you renew it in time."
+    - icon: "🔒"
+      title: "On paper, and off the grid"
+      items:
+        - "Printable labels and cards for your packets and jars, each with a code to scan."
+        - "One tap saves a sealed backup; a recovery card brings everything back."
+        - "Works fully offline, with no account. Your data stays on your phone unless you send it."
+    - icon: "🤝"
+      title: "Share and stay connected"
+      items:
+        - "Offer spare seed to give away, swap or sell — and see what others share."
+        - "Private messages to arrange a swap, person to person."
+        - "Vouch for people you've met and see who you can trust."
+        - "Make a plantaré promise: agree to return part of what you multiply."
+        - "Keep everything in sync across your own devices."
 values:
   title: "Why Tane is different"
   points: