Move RAG repository from rag-api to rag-data — consolidate data layer ownership

- Move IRagRepository, EfRagRepository, and VectorSerializer from rag-api/Data to rag-data/Repositories
- Add rag-api-models ProjectReference to rag-data.csproj for model type availability
- Delete rag-api/Data folder (no longer needed; all data access is now in rag-data)
- This aligns RAG with email-api and other services: all data code in the data project

Pattern: rag-api (API logic) → rag-data (repository, EF entities, migrations)

Co-Authored-By: Claude Haiku 4.5 <noreply@anthropic.com>

Apis/myai-data/Migrations/20260528120000_DeleteMigratedTemplates.cs

@@ -1,4 +1,5 @@
 using Microsoft.EntityFrameworkCore.Migrations;
+using MyAi.Data;
 
 #nullable disable
 
@@ -10,8 +11,8 @@ namespace MyAi.Data.Migrations
         /// <inheritdoc />
         protected override void Up(MigrationBuilder migrationBuilder)
         {
-            migrationBuilder.Sql("DELETE FROM [myAi].[Templates] WHERE [Key] LIKE 'email.%'");
-            migrationBuilder.Sql("DELETE FROM [myAi].[Templates] WHERE [Key] LIKE 'ai.%'");
+            migrationBuilder.Sql($"DELETE FROM [{MigrationConstants.SchemaName}].[Templates] WHERE [Key] LIKE 'email.%'");
+            migrationBuilder.Sql($"DELETE FROM [{MigrationConstants.SchemaName}].[Templates] WHERE [Key] LIKE 'ai.%'");
         }
 
         /// <inheritdoc />