Commit MWS backend source tree

The ASP.NET Core solution (mws.api/mws.application/mws.domain/
mws.infrastructure) existed only as untracked working files. Adding
it to version control, plus a .gitignore for build output and local
tooling directories, so the CQRS/mediator refactor plan has a real
git history to branch and diff against.

mws.infrastructure/Persistence/Repositories/RepositoryBase.cs

@@ -0,0 +1,13 @@
+using Microsoft.EntityFrameworkCore;
+using Mws.Application.Common.Repositories;
+
+namespace Mws.Infrastructure.Persistence.Repositories;
+
+public abstract class RepositoryBase<T>(AppDbContext db) : IRepository<T> where T : class
+{
+    protected readonly AppDbContext Db = db;
+    protected DbSet<T> Set => Db.Set<T>();
+
+    public void Add(T entity) => Set.Add(entity);
+    public void Remove(T entity) => Set.Remove(entity);
+}