[0.9.1] FORK_IA_UX v2: fix top-bar (visibility sheet) + Karvan module (ephemeral messages + WebRTC)

Navigation fixes:
- The bottom "Explore" sheet no longer blocks the top bar: closed state is
  visibility:hidden (out of hit-testing), so the top identity buttons and page
  content always receive taps (fixes "top buttons don't work").
- Top bar is now identity only (logo, avatar). The Personal/Community filter
  moved into the Explore sheet, next to the hive, as a segmented control.

New module "Karvan" (self-contained; inspired by karvan-protocol ephemeral rooms):
- Ephemeral/temporary chat rooms held only in RAM, self-destructing on idle
  (30 min) / absolute (2 h) TTL — nothing is written to disk.
- Server relay chat (RAM + polling) as the reliable path, plus a WebRTC
  data-channel layer (perfect negotiation, HTTP signaling mailbox) for instant
  P2P delivery; degrades to the relay if WebRTC is unavailable. Data-channel
  only (no camera/mic) so no wrapper permission changes are needed.
- Files: models/karvan_model.js, views/karvan_view.js, client/public/js/karvan.js;
  routes /karvan* + karvanMod config + nav entry (network) + karvanTitle i18n (11 langs).

Additive and gated by OASIS_MOBILE / karvanMod; Linux and the UX_OASIS branch untouched.

src/views/karvan_view.js

@@ -0,0 +1,91 @@
+"use strict";
+// Vista del módulo KARVAN (mensajes temporales + WebRTC). El chat va por relay servidor (RAM,
+// autodestrucción) y, si conectan pares, por data-channel WebRTC (instantáneo). El <script> solo
+// se carga en la página de sala; el WebRTC usa data-channel (sin cámara/mic => sin permisos extra).
+
+const { div, section, h2, h3, p, a, form, input, button, span, ul, li, script, label } =
+  require("../server/node_modules/hyperaxe");
+const { template, i18n } = require("./main_views");
+
+const fmtExpires = (expiresAt) => {
+  const mins = Math.max(0, Math.round((expiresAt - Date.now()) / 60000));
+  if (mins >= 60) return `${Math.floor(mins / 60)}h ${mins % 60}m`;
+  return `${mins}m`;
+};
+
+const shortId = (id) => {
+  id = String(id || "?");
+  return id.startsWith("@") ? id.slice(1, 7) : id.slice(0, 6);
+};
+exports.karvanShortId = shortId;
+
+const renderMsg = (m) =>
+  li({ class: "karvan-msg", "data-seq": String(m.seq), "data-mid": m.mid || "" },
+    span({ class: "km-from" }, shortId(m.from)),
+    span({ class: "km-text" }, m.text)
+  );
+
+const ttlOpt = (val, lbl, checked) =>
+  label({ class: "karvan-ttl-opt" },
+    input(Object.assign({ type: "radio", name: "ttl", value: val }, checked ? { checked: "checked" } : {})),
+    span(lbl)
+  );
+
+exports.karvanView = (rooms, params = {}) =>
+  template(
+    i18n.karvanTitle || "Karvan",
+    section({ class: "karvan-intro" },
+      h2("Karvan · " + (i18n.karvanEphemeral || "Ephemeral rooms")),
+      p({ class: "karvan-sub" },
+        i18n.karvanBlurb ||
+          "Temporary rooms that self-destruct. Messages live only in memory — never saved — and vanish when the room expires. Real-time over WebRTC when a peer connects.")
+    ),
+    section({ class: "karvan-create" },
+      form({ method: "POST", action: "/karvan/create" },
+        input({ type: "text", name: "title", placeholder: i18n.karvanRoomName || "Room name (optional)", maxlength: "80", autocomplete: "off" }),
+        div({ class: "karvan-ttl" },
+          span({ class: "karvan-ttl-lbl" }, i18n.karvanTtl || "Self-destruct in:"),
+          ttlOpt("30", "30m", true), ttlOpt("120", "2h", false), ttlOpt("480", "8h", false)
+        ),
+        button({ type: "submit" }, i18n.karvanCreate || "Create ephemeral room")
+      )
+    ),
+    section({ class: "karvan-list" },
+      h3(i18n.karvanActive || "Active rooms"),
+      rooms && rooms.length
+        ? ul({ class: "karvan-rooms" },
+            ...rooms.map((r) =>
+              li(
+                a({ href: "/karvan/" + r.id, class: "karvan-room-item" },
+                  span({ class: "kr-title" }, r.title || "room " + r.id.slice(0, 6)),
+                  span({ class: "kr-meta" }, `${r.count} · ⏳ ${fmtExpires(r.expiresAt)}`)
+                )
+              )
+            )
+          )
+        : p({ class: "karvan-empty" }, i18n.karvanNone || "No active rooms. Create one — it disappears on its own.")
+    )
+  );
+
+exports.karvanRoomView = (room, messages, params = {}) =>
+  template(
+    "Karvan · " + (room.title || room.id.slice(0, 6)),
+    section({ class: "karvan-room", "data-room": room.id, "data-self": params.selfId || "" },
+      div({ class: "karvan-room-head" },
+        a({ href: "/karvan", class: "karvan-back" }, "‹ " + (i18n.karvanRooms || "Rooms")),
+        span({ class: "karvan-room-title" }, room.title || "room " + room.id.slice(0, 6)),
+        span({ class: "karvan-expire", id: "karvan-expire" }, "⏳ " + fmtExpires(room.expiresAt))
+      ),
+      div({ class: "karvan-live", id: "karvan-live" },
+        span({ class: "kl-dot" }),
+        span({ class: "kl-txt", id: "karvan-live-txt" }, i18n.karvanRelay || "server relay")
+      ),
+      ul({ class: "karvan-msgs", id: "karvan-msgs" }, ...(messages || []).map(renderMsg)),
+      form({ class: "karvan-compose", method: "POST", action: "/karvan/" + room.id + "/msg", id: "karvan-form" },
+        input({ type: "hidden", name: "from", value: params.selfId || "" }),
+        input({ type: "text", name: "text", id: "karvan-text", placeholder: i18n.karvanSay || "Temporary message…", maxlength: "2000", autocomplete: "off" }),
+        button({ type: "submit" }, i18n.karvanSend || "Send")
+      )
+    ),
+    script({ src: "/js/karvan.js", defer: "defer" })
+  );