fix(tests): update OAuth tests to use correct signature URL path

Change test URLs from '/sign?doc=' to '/?doc=' to match the correct
frontend route after the URL path correction in reminder emails.

Updated base64 encoded state in callback test:
- Old: L3NpZ24_ZG9jPXRlc3Q (decodes to /sign?doc=test)
- New: Lz9kb2M9dGVzdA (decodes to /?doc=test)

docs/integrations/google-doc/GOOGLE_INTEGRATION.md

@@ -52,7 +52,7 @@ function onOpen() {
  * Redirige vers la page de validation Ackify
  */
 function validateReading() {
-  const signUrl = `${ACKIFY_BASE_URL}/sign?doc=${DOCUMENT_ID}&referrer=${encodeURIComponent(getDocumentUrl())}`;
+  const signUrl = `${ACKIFY_BASE_URL}/?doc=${DOCUMENT_ID}&referrer=${encodeURIComponent(getDocumentUrl())}`;
   
   const html = `
     <div style="padding: 20px; font-family: Arial, sans-serif;">

docs/integrations/google-doc/exemple/appscript/Code.gs

@@ -19,7 +19,7 @@ function getSidebarHtml() {
 function openSignature() {
   var doc = DocumentApp.getActiveDocument();
   var docId = doc.getId();
-  var url = "https://sign.neodtx.com/sign?doc=" + encodeURIComponent(docId);
+  var url = "https://sign.kolapsis.com/?doc=" + encodeURIComponent(docId);
 
   var html = '<style>html,body{height:100%;margin:0;padding:0}</style>' +
             '<iframe src="' + url + '" ' +