docs(savanna): add database secret walkthrough video

Embed Savanna_Database_Secrets.mp4 in the create-database-secret guide to
demonstrate the flow in Savanna.

Author: ngarakapati

modules/savanna/modules/administration/images/Savanna_Database_Secrets.mp4

@@ -15,6 +15,9 @@ Use one when you configure TigerGraph MCP or other clients that talk to the data
 Treat database secrets like passwords. Do not commit them to source control.
 ====
 
+.Watch: create a database secret in Savanna
+video::Savanna_Database_Secrets.mp4[width=760]
+
 For secrets in Admin Portal or GraphStudio, see https://www.tigergraph.com/docs/gui/4.3/admin-portal/management/user-management/#manage-secrets[Manage secrets^] and https://www.tigergraph.com/docs/tigergraph-server/4.3/user-access/user-credentials/#_create_a_secret[Create a secret^].
 
 == Where to go next