Staged undo, built-ins window, machine warnings; raw and dynamic set fixes

- Undo is staged like any edit: in review mode the web UI's Undo, and hc
  history undo with -C or HOUSECARL_CHANGESET, add a revert operation
  that checks, when replayed, that nothing it touches changed since;
  applied, History links the entries. Imports and takeovers still can't
  be staged.
- The rules page sums up a chain's built-ins in one line; a window lists
  them with what they do and their hits, and switches them.
- Warnings about the machine (dashboard, hc status): nftables.service
  enabled (it loads /etc/nftables.conf at boot and flushes every table
  when stopped), and the imported table still in force beside
  Housecarl's. The docs say to disable nftables.service but not stop it.
- A raw rule with other fields set is refused (raw_conflict) instead of
  silently ignoring them; the rule dialog's nftables section hides what
  it replaces, and the importer's raw rules carry only their text.
- A dynamic set with configured entries is refused
  (set_dynamic_entries): they were silently ignored. The set dialog
  shows entries or the entry timeout, as fits.
- The rule dialog's chain choices are just the chains' names.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/importer/importer.go

@@ -39,6 +39,8 @@ type Input struct {
 // Result is the imported configuration and what to know about it.
 type Result struct {
 	State *model.State
+	// Table is the table imported ("inet main").
+	Table string
 	Notes []string
 	// Raw lists the rules that became raw rules.
 	Raw []string
@@ -206,7 +208,7 @@ func Import(in Input) (*Result, error) {
 	im.run()
 	im.nameForwards()
 	im.st.Renumber()
-	return &Result{State: im.st, Notes: im.notes, Raw: im.raw}, nil
+	return &Result{State: im.st, Table: im.table.Family + " " + im.table.Name, Notes: im.notes, Raw: im.raw}, nil
 }
 
 func tableList(ts []nftTable) string {
@@ -1464,7 +1466,8 @@ func (im *importer) rawRule(r *model.Rule, p *parsed) {
 	if r.Action == "" {
 		r.Action = model.ActionAccept
 	}
-	r.Match, r.Raw = model.Match{}, text
+	// Only the text counts: what was parsed of it goes.
+	*r = model.Rule{ID: r.ID, Chain: r.Chain, Position: r.Position, Comment: r.Comment, Action: r.Action, Raw: text}
 	im.st.Rules = append(im.st.Rules, r)
 	why := strings.Join(p.unsupported, ", ")
 	if why == "" {