Update pin input type to password to mask pin and match dumbwareio products (#33)

public/login.html

@@ -81,7 +81,7 @@
             
             for (let i = 0; i < length; i++) {
                 const input = document.createElement('input');
-                input.type = 'text';
+                input.type = 'password';
                 input.className = 'pin-digit';
                 input.maxLength = 1;
                 input.pattern = '[0-9]';