UX/UI redesign for the mobile WebView

- Compact top bar (logo, OASIS, user avatar with default fallback).
- Fixed bottom navigation (Search, Inbox, Write, Activity + Peers/Invites) with active state.
- Removed duplicated header nav buttons on mobile.
- Personal/Community submenus: single-open accordion.
- Activity filters grouped into quick modes + collapsible thematic groups.
- Private messages rendered as chat bubbles on mobile.
- Text fixes, full-width stacked tables, touch feedback; Activity group labels in 11 locales.
Mobile-scoped (mobile.css + views); desktop unaffected.

src/client/public/js/oasis-mobile-nav.js

@@ -0,0 +1,36 @@
+(function () {
+  function mark() {
+    var p = (location.pathname || "/").replace(/\/+$/, "") || "/";
+    var links = document.querySelectorAll(".oasis-bottombar a.bb-item");
+    var best = null, bestLen = -1;
+    links.forEach(function (a) {
+      var h = (a.getAttribute("href") || "").replace(/\/+$/, "") || "/";
+      if (h === "/") return;
+      if (p === h || p.indexOf(h + "/") === 0) {
+        if (h.length > bestLen) { best = a; bestLen = h.length; }
+      }
+    });
+    if (best) best.classList.add("current");
+  }
+
+  function onToggle(e) {
+    var t = e.target;
+    if (!t || !t.classList || !t.classList.contains("oasis-nav-toggle")) return;
+    if (!t.checked) return;
+    var group = t.closest(".oasis-nav-group");
+    var scope = group && group.parentElement;
+    if (!scope) return;
+    var others = scope.querySelectorAll(
+      ":scope > .oasis-nav-group > .oasis-nav-toggle"
+    );
+    others.forEach(function (o) { if (o !== t) o.checked = false; });
+  }
+
+  function init() {
+    mark();
+    document.addEventListener("change", onToggle);
+  }
+
+  if (document.readyState !== "loading") init();
+  else document.addEventListener("DOMContentLoaded", init);
+})();