fix: resolve merge conflict in database.py

Merge origin/main into branch, resolving conflict in app/database.py.
Combined improvements from both branches:
- Keep pool_pre_ping=True and structured variable approach from feature branch
- Add explicit QueuePool import and poolclass assignment from main

.env.demo

@@ -457,6 +457,15 @@ ONEDRIVE_TENANT_ID=common
 ONEDRIVE_REFRESH_TOKEN=your-refresh-token
 ONEDRIVE_FOLDER_PATH=Documents/Uploads
 
+# SharePoint
+SHAREPOINT_CLIENT_ID=your-client-id
+SHAREPOINT_CLIENT_SECRET=your-client-secret
+SHAREPOINT_TENANT_ID=common
+SHAREPOINT_REFRESH_TOKEN=your-refresh-token
+SHAREPOINT_SITE_URL=https://tenant.sharepoint.com/sites/sitename
+SHAREPOINT_DOCUMENT_LIBRARY=Documents
+SHAREPOINT_FOLDER_PATH=Uploads
+
 # WebDAV
 # WEBDAV_ENABLED=true  # Set to false to disable WebDAV uploads without removing credentials
 WEBDAV_URL=https://webdav.example.com/path