Show number of credentials per folder and overall dashboard stats

Problem Currently, when browsing folders in Vaultwarden, the UI does not display how many credentials/items are stored in each folder. The same applies to the general vault view, there is no visible total count of stored accounts. For users with many stored credentials, it would be helpful to quickly understand how many items exist in a folder or in the vault overall. Proposed Solution Add a credential/item counter in the UI. Examples: • Show the number of credentials next to each folder name • Show the total number of credentials in the vault • Optionally provide a small dashboard or statistics section Example ideas for a dashboard: • Total number of credentials • Number of folders • Possibly other simple vault statistics Inspiration A similar concept can be seen in the dashboard used by Linkwarden, which provides a quick overview of stored items. Benefits • Better overview of stored credentials • Easier vau…