fix(backend): give track titles room to breathe

Titles were capped at 50 characters and the YouTube provisioner silently cut
them there, which mangles anything with a feature or a remix suffix. Albums
are about to make that far more visible, so the column now holds 200.

backend/Musify.Api/Validators/Tracks/CreateTrackRequestValidator.cs

@@ -9,7 +9,7 @@ public sealed class CreateTrackRequestValidator : AbstractValidator<CreateTrackR
     {
         RuleFor(x => x.Title)
             .NotEmpty()
-            .MaximumLength(50);
+            .MaximumLength(200);
 
         RuleFor(x => x.PictureIntentId)
             .NotEmpty();