Add Google Drive authorization processing and error handling templates

- Implemented `google_drive_callback.html` for processing Google Drive authorization, including UI for success and error states.
- Added JavaScript functionality for exchanging authorization codes, saving settings, and handling folder selection.
- Created `google_drive_callback_error.html` to display error messages during the authorization process.

frontend/templates/dropbox_callback.html

@@ -185,12 +185,18 @@ document.addEventListener('DOMContentLoaded', function() {
     document.getElementById('processing-message').classList.add('hidden');
     document.getElementById('error-container').classList.remove('hidden');
     document.getElementById('error-message').innerText = message;
+    
+    // Hide the spinner when showing error
+    document.querySelector('.animate-spin').parentNode.classList.add('hidden');
   }
   
   function showSuccess(refreshToken, appKey, appSecret, folderPath) {
     document.getElementById('processing-message').classList.add('hidden');
     document.getElementById('success-container').classList.remove('hidden');
     
+    // Hide the spinner when showing success
+    document.querySelector('.animate-spin').parentNode.classList.add('hidden');
+    
     // Update the environment variables pre block with the new token
     const envVarsCode = document.querySelector('#env-vars code');
     if (envVarsCode) {