Add user avatar and profile feature, consolidate Auth and UserManagement features (#257)

web/backend/Database/Database.Seed/DatabaseHelpers/AvatarGenerator.cs

@@ -0,0 +1,27 @@
+using SkiaSharp;
+
+namespace Database.Seed.DatabaseHelpers;
+
+/// <summary>Generates minimal solid-color square avatars for seeded users.</summary>
+public static class AvatarGenerator
+{
+    private const int SizePx = 128;
+
+    /// <summary>
+    ///     Generates a deterministic solid-color PNG avatar, with the color derived from
+    ///     <paramref name="userId" />.
+    /// </summary>
+    public static byte[] GeneratePng(Guid userId)
+    {
+        byte[] idBytes = userId.ToByteArray();
+        SKColor color = new(idBytes[0], idBytes[1], idBytes[2]);
+
+        using SKBitmap bitmap = new(SizePx, SizePx);
+        bitmap.Erase(color);
+
+        using SKImage image = SKImage.FromBitmap(bitmap);
+        using SKData data = image.Encode(SKEncodedImageFormat.Png, quality: 100);
+
+        return data.ToArray();
+    }
+}