feat(setup): show running build version in the Setup tab bar

CI already computes <branch>-<short-sha> for image tags but never
surfaced it anywhere reachable from the app, so there was no way to
tell what's actually deployed on a booth without cross-referencing
komodo/resources.toml's TAG by hand.

Thread it through: CI passes BUILD_VERSION as a Docker build-arg,
the Dockerfile captures it as a runtime env var, GET /api/version
(gated by the existing site:read permission) exposes it, and the
Setup page's tab bar shows it right-aligned, muted, absent entirely
on a local/dev build with no CI-supplied value.

Claude-Session: https://claude.ai/code/session_01FWncR69HgGPuei1dLrW3cU

apps/web/src/api.ts

@@ -253,6 +253,15 @@ export async function fetchBackupStatus(): Promise<BackupStatus> {
   return apiFetch("/api/backup/status");
 }
 
+export interface VersionInfo {
+  /** "<branch>-<short-sha>" baked in at image build time; null on a local/dev build. */
+  buildVersion: string | null;
+}
+
+export async function fetchVersion(): Promise<VersionInfo> {
+  return apiFetch("/api/version");
+}
+
 export interface BackupConfigPatch {
   /** "" clears the target. Omit a field to leave it unchanged; null resets retention to default. */
   targetDir?: string | null;

apps/web/src/router.tsx

@@ -14,6 +14,7 @@ import {
   can,
   closeShift,
   fetchShiftReport,
+  fetchVersion,
   logout,
   openShift,
   setLanguagePref,
@@ -94,6 +95,17 @@ function SetupTab({ to, label, exact = false }: { to: string; label: string; exa
   );
 }
 
+/** The running deploy's "<branch>-<short-sha>" (matches the Komodo Stack's TAG in
+ *  komodo/resources.toml), gated the same as the "Park" tab (site:read) since it's the
+ *  same kind of read-only app metadata. Renders nothing if the value isn't known (e.g. a
+ *  local/dev build with no CI-supplied BUILD_VERSION) rather than showing an empty badge. */
+function VersionBadge() {
+  const q = useQuery({ queryKey: ["version"], queryFn: fetchVersion, staleTime: Infinity });
+  const version = q.data?.buildVersion;
+  if (!version) return null;
+  return <span className="ml-auto shrink-0 pl-3 text-[0.7rem] text-term-muted">{version}</span>;
+}
+
 /** Setup layout — the config hub. Renders a permission-gated tab bar and the active
  *  tab's screen via <Outlet>. Each tab is a child route (its own URL + guard), so
  *  deep links and the back button work and a denied tab redirects to the booth. */
@@ -112,6 +124,7 @@ function SetupLayout() {
         {show("recyclebin:read") && <SetupTab to="/setup/recycle-bin" label={t("nav.recycleBin")} />}
         {show("log:read") && <SetupTab to="/setup/logs" label={t("nav.logs")} />}
         {show("backup:read") && <SetupTab to="/setup/backup" label={t("nav.backup")} />}
+        {show("site:read") && <VersionBadge />}
       </nav>
       <Outlet />
     </div>