- lib/common: stamp_applied() now records a _last_applied_config
snapshot alongside the hash; strip_apply_meta() centralizes
bookkeeping-key stripping; deep_diff() reports field-level changes
- state collectors (dnsmasq/nginx/wireguard/networkd) expose
pending_diff so the dashboard can show exactly which fields
changed since the last apply (wireguard diff excludes
private_key paths)
- dashboard pending-changes card renders per-change lines with a
generic fallback when no snapshot is recorded
- firewall: firewalld built-in zones no longer flagged as
unmanaged; public-zone masquerade skipped in pending changes
since apply drives it via nftables propagation
- schema: PendingChange TypedDict; pending_diff on DnsmasqStatus /
WgStatus; tests in test_common.py, test_firewall.py, test_state.py
