refactor code and improve daily cache handling of deleted VMs

README.md

@@ -27,6 +27,13 @@ Configuration now lives in the YAML settings file. By default the service reads
 vctp -settings /path/to/vctp.yml
 ```
 
+If you just want to run a single inventory snapshot across all configured vCenters and
+exit (no scheduler/server), use:
+
+```shell
+vctp -settings /path/to/vctp.yml -run-inventory-once
+```
+
 ### Database Configuration
 By default the app uses SQLite and creates/opens `db.sqlite3`. You can opt into PostgreSQL
 by updating the settings file: