feat: Implement QueryExecutor for executing queries using IQueryable

- Added a record `QueryExecutor<TEntity>` implementing `IQueryExecutor<TEntity>` for executing common query operations like First, Single, and ToList both synchronously and asynchronously.
- Methods leverage the IQueryable interface to perform database queries for entity types.

EnvelopeGenerator.Infrastructure/QueryExecutor.cs

@@ -0,0 +1,34 @@
+using EnvelopeGenerator.Application.Contracts.SQLExecutor;
+using Microsoft.EntityFrameworkCore;
+
+namespace EnvelopeGenerator.Infrastructure;
+
+public record QueryExecutor<TEntity>(IQueryable<TEntity> Queryable) : IQueryExecutor<TEntity>
+{
+    public TEntity First() => Queryable.First();
+
+    public Task<TEntity> FirstAsync() => Queryable.FirstAsync();
+
+    public TEntity? FirstOrDefault() => Queryable.FirstOrDefault();
+
+
+    public Task<TEntity?> FirstOrDefaultAsync() => Queryable.FirstOrDefaultAsync();
+
+
+    public TEntity Single() => Queryable.Single();
+
+
+    public Task<TEntity> SingleAsync() => Queryable.SingleAsync();
+
+
+    public TEntity? SingleOrDefault() => Queryable.SingleOrDefault();
+
+
+    public Task<TEntity?> SingleOrDefaultAsync() => Queryable.SingleOrDefaultAsync();
+
+
+    public IEnumerable<TEntity> ToList() => Queryable.ToList();
+
+
+    public async Task<IEnumerable<TEntity>> ToListAsync() => await Queryable.ToListAsync();
+}