feat(ui): mobile mesh tabs, AIUI-style audio player, cloud grid + map fixes

UI (this session):
- Global audio player now scales the whole interface into the space above it
  on desktop (sidebar + main) and docks directly above the tab bar on mobile;
  it stays visible while navigating.
- Mesh mobile redesign: floating Chat / BTC / Dead Man / AI / Map tab strip
  with a single fixed, internally-scrolling pane (page no longer scrolls);
  tabs hide while a conversation is open; floating back button; collapsible
  Device panel (starts collapsed); keyboard-aware conversation sizing via
  VisualViewport so the chat sits just above the keyboard.
- Cloud file grid: uniform 4/3 card heights (folders + images match).
- Swipe left/right switches tabs on the Apps and Web5 screens.
- Map tool fills its pane (no bottom gap); fix skewed Share Location toggle
  on mobile (global min-height rule was deforming the switch).
- Trim redundant helper copy from the mesh AI tab.

Also bundles pre-existing in-progress work that was already in the tree:
mesh listener/session + wallet + container + bitcoin-status backend changes,
docker UI updates, and assorted other UI tweaks.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

core/archipelago/src/api/handler/content.rs

@@ -146,7 +146,9 @@ impl ApiHandler {
             Ok(content_server::ServeResult::Forbidden) => Ok(build_response(
                 StatusCode::FORBIDDEN,
                 "application/json",
-                hyper::Body::from(r#"{"error":"Access denied — federation peer required"}"#),
+                hyper::Body::from(
+                    r#"{"error":"This file is shared with the host's federation peers only. Federate with that node (exchange invites) so it recognizes you, then try again."}"#,
+                ),
             )),
             Ok(content_server::ServeResult::NotFound) | Err(_) => Ok(build_response(
                 StatusCode::NOT_FOUND,