feat: add .creds files for erpnext, teable, tubearchivist, storyteller

Write credentials to ~/appname.creds matching existing convention
(affine, discourse, ente). Update CT scripts to reference .creds.

- erpnext: admin pass, db root pass
- teable: db pass, secret key
- tubearchivist: admin pass, ES pass
- storyteller: secret key

install/storyteller-install.sh

@@ -48,6 +48,11 @@ NODE_ENV=production
 NEXT_TELEMETRY_DISABLED=1
 EOF
 mkdir -p /opt/storyteller/data
+{
+  echo "Storyteller Credentials"
+  echo "======================="
+  echo "Secret Key: ${STORYTELLER_SECRET_KEY}"
+} >~/storyteller.creds
 msg_ok "Set up Storyteller"
 
 msg_info "Building Storyteller"