feat: node info, build info and acrylic web theme

Squash of recent dev work: return_session login, backend switcher, line
detail timeline, overview strips, node platform/country/ISP info with flags
and icons, build info (version, tag, time) behind site.show_build, and the
acrylic display theme.

backend/src/Monitor.Backend.Api/ApiModule.cs

@@ -97,6 +97,7 @@ public static class ApiModule
         QueryEndpoints.Map(publicGroup);
         LiveEndpoints.Map(publicGroup);
         HostEndpoints.Map(publicGroup);
+        NodeEndpoints.Map(publicGroup);
         CatalogEndpoints.Map(publicGroup);
 
         RouteGroupBuilder admin = app.MapGroup("/api/admin");
@@ -108,6 +109,7 @@ public static class ApiModule
         TaskEndpoints.Map(guarded);
         DataEndpoints.Map(guarded);
         SystemEndpoints.Map(guarded);
+        BuildEndpoints.Map(guarded);
 
         OpsEndpoints.Map(app);
         app.MapOpenApi("/openapi/v1.json");