refactor: standardize project names to Musify.* and flatten layout

- Flatten nested per-repo folders into flat Musify.* projects at root
- Rename assemblies/csproj: Domain->Musify.Domain, Application->Musify.Application,
  Infrastructure->Musify.Infrastructure, WebApi->Musify.Api, Worker->Musify.Worker,
  StreamingGateway->Musify.StreamingGateway
- Rename WebApi.* namespaces to Musify.Api.*
- Update all ProjectReference paths and the solution file
- Consolidate stray per-repo dotfiles; add root .gitattributes
- Move flutter client out to _archive

Musify.Application/Users/Handlers/GetUsersQueryHandler.cs

@@ -0,0 +1,35 @@
+using Ardalis.Result;
+using Mediator;
+using Microsoft.EntityFrameworkCore;
+using Musify.Application.Pagination;
+using Musify.Application.Users.Queries;
+using Musify.Application.Users.Responses;
+using X.PagedList.EF;
+using Musify.Application.Contracts;
+
+namespace Musify.Application.Users.Handlers
+{
+    public class GetUsersQueryHandler(IDatabase database)
+        : IQueryHandler<GetUsersQuery, Result<PaginatedResponse<UserApplicationResponse> > >
+    {
+        public async ValueTask<Result<PaginatedResponse<UserApplicationResponse> >> Handle(GetUsersQuery request, CancellationToken cancellationToken)
+        {
+            var user = database.Users
+                .AsNoTracking()
+                .AsQueryable();
+
+            if (request.UsernameSearch is not null)
+            {
+                var normalizedUsername = request.UsernameSearch.Trim().ToUpperInvariant();
+                user = user.Where(u => u.NormalizedName.Contains(normalizedUsername));
+            }
+
+            var totalCount = await user.CountAsync(cancellationToken);
+            var pagedUser = await user
+                .Select(u => UserApplicationResponse.FromEntity(u))
+                .ToPagedListAsync(request.PageNumber, request.PageSize, totalCount, cancellationToken);
+
+            return Result.Success(PaginatedResponse<UserApplicationResponse>.FromPagedList(pagedUser));
+        }
+    }
+}