Add shared pagination, projections and ownership helpers; simplify query and command handlers

backend/Core/Musify.Application/Users/Responses/UserProfileResponse.cs

@@ -0,0 +1,16 @@
+using System.Text.Json.Serialization;
+using Musify.Application.Serialization;
+
+namespace Musify.Application.Users.Responses;
+
+public record UserProfileResponse(
+    [property: JsonConverter(typeof(LongAsStringConverter))] long Id,
+    string Name,
+    string? FirstName,
+    string? SecondName,
+    string? ProfilePictureUrl,
+    DateTime CreatedAt,
+    int FollowersCount,
+    int FollowingCount,
+    bool IsFollowing,
+    bool CanViewFollowers);