Restructure solution layout by module

src/Signals/StellaOps.Signals/Storage/Models/CallgraphArtifactSaveRequest.cs

@@ -0,0 +1,12 @@
+namespace StellaOps.Signals.Storage.Models;
+
+/// <summary>
+/// Context required to persist a callgraph artifact.
+/// </summary>
+public sealed record CallgraphArtifactSaveRequest(
+    string Language,
+    string Component,
+    string Version,
+    string FileName,
+    string ContentType,
+    string Hash);