feat(block2): market screen — discover seeds near you (offers UI)

Wires the 'coming soon' market card to a real discovery screen (mockups 04/05):
- MarketScreen: opens an OfferTransport lazily; local-first, so it degrades to a
  human 'set up sharing' prompt when no relay/area is set or the net is down.
- Discovers offers by the saved coarse area, lists them with human reciprocity
  labels (gift/swap/for sale), 'near you' (never exact location), price only for
  sales. Config sheet to set area + community servers (no bundled public relays).
- Threaded via TaneApp(social, socialSettings) — null keeps the card 'coming
  soon' (so Block 1 tests pass unchanged); main wires it live.
- i18n en/es/pt (market.*), reuses share.* for type labels.

3 market widget tests + home tests green; app_seeds analyzes clean.

apps/app_seeds/lib/i18n/en.i18n.json

@@ -327,5 +327,23 @@
     "cutting": { "singular": "cutting", "plural": "cuttings" },
     "grams": { "singular": "gram", "plural": "grams" },
     "count": { "singular": "seed", "plural": "seeds" }
+  },
+  "market": {
+    "title": "Seeds near you",
+    "subtitle": "What others are sharing nearby",
+    "notSetUp": "Sharing isn't set up yet",
+    "notSetUpBody": "Add a community server and your area to see and share seeds nearby. Everything stays coarse — never your exact address.",
+    "setUp": "Set up sharing",
+    "searching": "Looking around your area…",
+    "empty": "No seeds shared near you yet",
+    "near": "Near you",
+    "configTitle": "Sharing setup",
+    "areaLabel": "Area code",
+    "areaHelp": "Kept coarse on purpose — roughly your zone, never an exact spot.",
+    "serversLabel": "Community servers",
+    "serversHelp": "One address per line — run by seed networks or collectives, not a company.",
+    "save": "Save",
+    "saved": "Saved",
+    "wanted": "Wanted"
   }
 }