fix(webhook): keep line breaks in Telegram rich messages (#39650)

Restore the old layout by converting line breaks (`\n`, `\r\n`, `\r`) to `<br>`
in `createTelegramPayloadHTML`, after sanitizing, covering every Telegram
payload type at once.

Fixes https://github.com/go-gitea/gitea/issues/39649

services/webhook/telegram.go

@@ -201,9 +201,12 @@ func (telegramConvertor) WorkflowJob(p *api.WorkflowJobPayload) (TelegramPayload
 
 func createTelegramPayloadHTML(msgHTML string) TelegramPayload {
 	// https://core.telegram.org/bots/api#formatting-options
+	sanitized := strings.TrimSpace(string(markup.Sanitize(msgHTML)))
+	// Rich messages collapse bare newlines like HTML, so keep line breaks as <br>.
+	sanitized = strings.NewReplacer("\r\n", "<br>", "\r", "<br>", "\n", "<br>").Replace(sanitized)
 	return TelegramPayload{
 		RichMessage: InputRichMessage{
-			HTML: strings.TrimSpace(string(markup.Sanitize(msgHTML))),
+			HTML: sanitized,
 		},
 	}
 }