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>

cmd/hc/rules.go

@@ -285,6 +285,9 @@ func ruleCmd() *cobra.Command {
 					}
 					extra := ruleExtras(r)
 					action := r.Action
+					if r.Raw != "" {
+						action = "-" // the text's own
+					}
 					if r.Log {
 						action += "+log"
 					}
@@ -298,7 +301,11 @@ func ruleCmd() *cobra.Command {
 	}
 	cmd.AddCommand(ls)
 	cmd.AddCommand(showCmd("rules", "rule", func(w io.Writer, r model.Rule) {
-		fmt.Fprintf(w, "ID:\t%d\nChain:\t%s\nMatch:\t%s%s\nAction:\t%s\n", r.ID, r.Chain, describe(r.Match), ruleExtras(r), r.Action)
+		if r.Raw == "" {
+			fmt.Fprintf(w, "ID:\t%d\nChain:\t%s\nMatch:\t%s%s\nAction:\t%s\n", r.ID, r.Chain, describe(r.Match), ruleExtras(r), r.Action)
+		} else {
+			fmt.Fprintf(w, "ID:\t%d\nChain:\t%s\n", r.ID, r.Chain)
+		}
 		if r.Raw != "" {
 			fmt.Fprintf(w, "Raw:\t%s\n", r.Raw)
 		}