swarm-ui, hive dashboard, agent page: one profile menu with the signed-in user, avatar and authelia links

The swarm UI's user menu moves to @hive/shared and takes the whoami URL and
authelia's URL as props; the swarm UI keeps a thin wrapper, and the hive
dashboard and the per-agent page mount the same component. The dashboard's
nginx vhost proxies /api/whoami to authelia (the agent page is served from
the same vhost), and hive-c0re's state carries authelia_public_url, set from
services.hyperhive.swarm.authelia.url. The agent page shows the menu only
behind the gateway.

docs/web-ui/agent.md

@@ -70,6 +70,13 @@ at a given viewport width. Two columns:
     unprivileged process can't make directly).
   - **Inbox / todos pills** (`📬 inbox · N` / `📋 todos · N`): hidden
     when empty; selecting it opens the matching flyout in the side panel.
+  - **Profile avatar**: the signed-in user's initial, opening a popover with
+    their name and links to authelia's settings and sign-out pages, as on the
+    dashboard (`AgentUserMenu.tsx`). It shows only behind the gateway, where
+    the page shares the dashboard's origin and session; opened on the agent's
+    own port there is no sign-in and no avatar. The name comes from the
+    dashboard's `/api/whoami`, authelia's URL from the dashboard's
+    `/api/state`.
   - **Links badge** (`🔗`): opens a popover listing `↑ dashboard`
     (back-link to the host dashboard, `${dashboardBase}`)
     followed by this agent's `agent_links()`-sourced navigation (stats,