fix: odit link + add ref in html mails

src/templates/welcome/de.html

@@ -335,7 +335,7 @@
 							><u
 								><strong
 									><a
-										href="http://ODIT.Services"
+										href="https://odit.services?ref=lfkmail"
 										rel="noopener noreferrer nofollow"
 										style="
 											color: #111827;

src/templates/welcome/en.html

@@ -330,7 +330,7 @@
 							><u
 								><strong
 									><a
-										href="http://ODIT.Services"
+										href="https://odit.services?ref=lfkmail"
 										rel="noopener noreferrer nofollow"
 										style="
 											color: #111827;