Make "Auto-fill on page load" editable on all platforms

At present, the “Auto-fill on page load” option can only be modified if you edit your vault via the browser extension. This is mildly inconvenient, since the interface for the extension is much harder to navigate than the full desktop application or the web interface.

It would be useful if this could be modified on any platform, even if that platform doesn’t support Auto-fill. At present, there is effectively hidden data for certain entries when viewing them on a platform that doesn’t support Auto-fill.

This isn’t without precident either, as the URI field and associated matching options are only relevant using the browser extension.