The statistics name RFC 9421 signatures

A delivery signed with RFC 9421 was counted under "other": its algorithm
(rsa-v1_5-sha256) has an underscore, which a signature name could not
hold. It is now counted as rfc9421:rsa-v1_5-sha256, as WordPress's are.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LsXgEaXee4GCU1hwYgPJXw

PrivaPub/Infrastructure/Statistics/Interactions.cs

@@ -95,7 +95,7 @@ namespace PrivaPub.Infrastructure.Statistics
 		[GeneratedRegex("^[a-z0-9][a-z0-9-]{0,39}$")]
 		private static partial Regex KebabWord();
 
-		[GeneratedRegex("^[a-z0-9][a-z0-9:-]{0,39}$")]
+		[GeneratedRegex("^[a-z0-9][a-z0-9:_-]{0,39}$")]
 		private static partial Regex SignatureName();
 
 		[GeneratedRegex("^[a-z0-9][a-z0-9:/+.-]{0,63}$")]