Fix File I/O chart showing 'Unknown' for unresolved file names (#633)

When sys.master_files LEFT JOIN misses (NULL file_name), fall back to
DB_{database_id} and File_{file_id} instead of generic 'Unknown'.
Chart labels now show e.g. 'MyDatabase.File_2' instead of
'MyDatabase.Unknown'.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: erikdarlingdata

Lite/Services/RemoteCollectorService.FileIo.cs

@@ -199,9 +199,9 @@ private static (string DatabaseName, string FileName, string FileType, string Ph
         int DatabaseId, int FileId) ReadFileIoRow(SqlDataReader reader)
     {
         return (
-            DatabaseName: reader.IsDBNull(0) ? "Unknown" : reader.GetString(0),
-            FileName: reader.IsDBNull(1) ? "Unknown" : reader.GetString(1),
-            FileType: reader.IsDBNull(2) ? "Unknown" : reader.GetString(2),
+            DatabaseName: reader.IsDBNull(0) ? $"DB_{reader.GetValue(13)}" : reader.GetString(0),
+            FileName: reader.IsDBNull(1) ? $"File_{reader.GetValue(14)}" : reader.GetString(1),
+            FileType: reader.IsDBNull(2) ? "UNKNOWN" : reader.GetString(2),
             PhysicalName: reader.IsDBNull(3) ? "" : reader.GetString(3),
             SizeMb: reader.IsDBNull(4) ? 0m : reader.GetDecimal(4),
             NumOfReads: reader.IsDBNull(5) ? 0L : reader.GetInt64(5),