Tineout with alternate file

**Is your feature request related to a problem? Please describe.**

I'm always frustrated when my passwords don't load because of the underlying file access beeing slow/unavailable.

For example, the nextcloud saf is quite unreliable on spotty connections. Sometimes it endlessly tries to update the file instead of returning the local cache.

**Describe the solution you'd like**
One idea i had that fullfills the 'do not store data' paradigm was to allow keepassdx to set it's own timeout, and then load a different password file. (Eg. a local copy)

This is something that should be the issue of the saf-provider, so i totally understand if you close this as out-of-scope.

**Describe alternatives you've considered**
It's already an alternative to other suggestions solving password files beeing unavailable

**Additional context**

Start by tracing KeePassDX’s SAF file-loading path and its behavior when a Nextcloud-backed file is slow or unavailable. Determine whether timeout control and loading a local alternate file belong in KeePassDX or the SAF provider; done requires an agreed scope and verified behavior.

Written by the indexing model from the issue text.