feat: import leftover student fields into notes and show them on the roster

Store leftover CSV columns on hidden student notes, move catalog import to /events/import, and persist Students index columns from Chapter Settings.

Co-authored-by: Cursor <cursoragent@cursor.com>

WebApp/Services/YearRolloverService.cs

@@ -12,17 +12,20 @@ public class YearRolloverService : IYearRolloverService
     private readonly AppDbContext _context;
     private readonly IDatabaseBackupService _backupService;
     private readonly IChapterSettingsWriter _chapterSettingsWriter;
+    private readonly INotesService _notesService;
     private readonly ILogger<YearRolloverService> _logger;
 
     public YearRolloverService(
         AppDbContext context,
         IDatabaseBackupService backupService,
         IChapterSettingsWriter chapterSettingsWriter,
+        INotesService notesService,
         ILogger<YearRolloverService> logger)
     {
         _context = context;
         _backupService = backupService;
         _chapterSettingsWriter = chapterSettingsWriter;
+        _notesService = notesService;
         _logger = logger;
     }
 
@@ -107,6 +110,8 @@ public class YearRolloverService : IYearRolloverService
                         $"Roster changed since the wizard loaded ({unexpected.Count} unexpected student(s): {names}). Reload the page and try again.");
                 }
 
+                await _notesService.SoftDeleteStudentNotesAsync(removalIds, cancellationToken);
+
                 _context.Students.RemoveRange(toRemove);
 
                 var promotionById = plan.Promotions.ToDictionary(p => p.Student.Id);