Add vault stats command and API endpoint

docs/advanced_cli.md

@@ -73,6 +73,7 @@ Manage the entire vault for a profile.
 | Import a vault | `vault import` | `seedpass vault import --file backup.json` |
 | Change the master password | `vault change-password` | `seedpass vault change-password` |
 | Lock the vault | `vault lock` | `seedpass vault lock` |
+| Show profile statistics | `vault stats` | `seedpass vault stats` |
 
 ### Nostr Commands
 
@@ -159,6 +160,7 @@ Code: 123456
 - **`seedpass vault import`** – Import a vault from an encrypted JSON file.
 - **`seedpass vault change-password`** – Change the master password used for encryption.
 - **`seedpass vault lock`** – Clear sensitive data from memory and require reauthentication.
+- **`seedpass vault stats`** – Display statistics about the active seed profile.
 
 ### `nostr` Commands