feat(dotnet): migrate core formulas, deploy tools, and blazor admin web app to .NET 10

src/dotnet/QuantEngine.Infrastructure/Data/DbConnectionFactory.cs

@@ -0,0 +1,25 @@
+using System.Data;
+using Npgsql;
+
+namespace QuantEngine.Infrastructure.Data
+{
+    public interface IDbConnectionFactory
+    {
+        IDbConnection CreateConnection();
+    }
+
+    public class DbConnectionFactory : IDbConnectionFactory
+    {
+        private readonly string _connectionString;
+
+        public DbConnectionFactory(string connectionString)
+        {
+            _connectionString = connectionString;
+        }
+
+        public IDbConnection CreateConnection()
+        {
+            return new NpgsqlConnection(_connectionString);
+        }
+    }
+}