Updated renew from 180 days to 3 years (1095 days)

It is true that the renew system may be automatic, but while it is manual, this reduces the operator's overhead (especially in officina informatica)

main.py

@@ -260,7 +260,7 @@ def get_gateway_config(fqdn):
 @app.route("/gateway/<fqdn>/renew", methods=["POST"])
 @auth.login_required
 def post_gateway_renew(fqdn):
-    os.environ["EASYRSA_CERT_EXPIRE"] = "180"  # days
+    os.environ["EASYRSA_CERT_EXPIRE"] = "1095"  # days
 
     r = os.system("easyrsa renew {} nopass".format(fqdn))
     if r != 0: