feat: build blazor client UI and PWA assets

src/ASTRAIN.Client/Services/UserContext.cs

@@ -0,0 +1,11 @@
+namespace ASTRAIN.Client.Services;
+
+public class UserContext
+{
+    public string UserId { get; private set; } = string.Empty;
+
+    public void SetUserId(string userId)
+    {
+        UserId = userId;
+    }
+}