Indicate file access to the File Provider

**Is your feature request related to a problem? Please describe.**
If storing the database in a cloud especially a self-hosted one it can take quite some time for it to be obtained.

**Describe the solution you'd like**
Upon opening KeePassDX it could already start downloading the most recent file in the background.

**Describe alternatives you've considered**
Waiting around

**Additional context**

No file or test is named. Start by tracing KeePassDX's Android file-opening and File Provider flow, then determine how opening the app could request the most recent cloud-hosted database in the background; done means the latest file is obtained before it is needed without blocking normal startup.

Written by the indexing model from the issue text.