Move models in separate projects

rag-api-models/RagChunkRecord.cs

@@ -0,0 +1,11 @@
+namespace Rag.Models
+{
+    public sealed class RagChunkRecord
+    {
+        public required string Id { get; init; }
+        public required string DocumentId { get; init; }
+        public int ChunkIndex { get; init; }
+        public required string Text { get; init; }
+        public required float[] Embedding { get; init; }
+    }
+}