Rework the nftables module so Webmin manages its saved nftables configuration as the source of truth instead of directly editing the live ruleset. Add an active ruleset view for inspecting live tables and importing copies into Webmin-managed config if needed, track managed and imported tables with metadata, and prevent externally managed tables from being overwritten during apply.
Co-authored-by: Copilot <copilot@github.com>
Fix nftables direct-mode operations so create, edit, delete, and move actions apply only the selected table instead of rewriting or applying the full ruleset. This avoids copying firewalld-owned rules, or any other externally managed rules, into Webmin’s save file and prevents operations from failing against externally managed tables. Also remove previously added unsafe full-ruleset flush action and keep Apply Configuration out of direct mode (will be further reworked).
