fix: proxy_recharge.ui Form Cancel button now resets form fields

The Form's Cancel button dispatches a 'cancel' event but no handler
existed. Added a bind to call reset_data() when Cancel is clicked,
which clears the form fields (username and amount inputs).

wwwroot/proxy_recharge.ui

@@ -68,6 +68,12 @@
                         "options": {
                             "url": "{{entire_url('/accounting/proxy_recharge_submit.dspy')}}"
                         }
+                    }, {
+                        "wid": "self",
+                        "event": "cancel",
+                        "actiontype": "method",
+                        "target": "self",
+                        "method": "reset_data"
                     }]
                 },
                 {