[Feature Request] Add configurable file page default sort order

Filestash currently supports default file page sort key via general.filepage_default_sort, but not default sort direction. This makes it hard to configure “Name A-Z” as the initial browser state.

Related possible bug- the current menu hardcodes the checkmark next to “Sort By Type” even when sort state is name.

Proposal:

• Add general.filepage_default_order with options asc/des.
• Export it as default_order in /api/config.
• Use getConfig("default_order", existing default) in filespage state_config.js.
• Render the sort dropdown checkmark from current state.sort/state.order instead of hardcoding it on Sort By Type.
• Preserve behavior of localStorage settings overriding defaults.

I can put together a PR if this looks fine. Should be relatively low-risk.