I am not familiar with the synology webserver, but one last thought, then:
You are probing
http://192.168.1.19/.well-known/carddav. So the .htacces file should be at
http://192.168.1.19/.htaccess and probably redirect to
/baikal/[card/cal].phpif you not already have additional fancier redirects.
EDIT: also, you could try opening
http://192.168.1.19/.well-known/carddav in a browser and see if you get a 404 error. What is strange though, is that the webserver doesn’t tell you it didn’t find the url, but sends a
405 Method Not Allowedwhich points to a configuration problem of the webserver.