Address ranges in address match lists (IPv4 and IPv6)

ACLs, views' match lists, options with address match lists and blocking
client groups take ranges such as 10.0.10.101-10.0.10.199 or
2001:db8::100-2001:db8::1ff (negated, or with spaces around the dash, too).
Jarl stores the range as written and writes the fewest prefixes that cover
exactly that range to named.conf, with the range as a comment. New package
internal/iprange; namedconf gets an AMRange element (a range used to parse
as an ACL name), ExpandRanges and statement comments. Mistakes are refused
when entered, validation sees what ranges cover, and IPv6 ranges in the
IPv4-mapped space get a warning. The web UI shows what a range becomes
while typing (GET /catalog/ranges).

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

internal/server/h_config.go

@@ -13,6 +13,7 @@ import (
 	"jarl/internal/catalog"
 	"jarl/internal/dnsname"
 	"jarl/internal/engine"
+	"jarl/internal/iprange"
 	"jarl/internal/model"
 	"jarl/internal/render"
 	"jarl/internal/rr"
@@ -554,6 +555,42 @@ func (s *Server) catalogRRTypes(w http.ResponseWriter, r *http.Request, p *auth.
 	return nil
 }
 
+// catalogRanges: GET /catalog/ranges?r=A-B,C-D shows the prefixes each
+// address range is written to named.conf as (the web UI shows them while
+// you type). Text that isn't a range is left out; a range with a mistake
+// comes back with its error.
+func (s *Server) catalogRanges(w http.ResponseWriter, r *http.Request, p *auth.Principal) error {
+	type rangeInfo struct {
+		Input    string   `json:"input"`
+		Range    string   `json:"range,omitempty"`
+		Prefixes []string `json:"prefixes,omitempty"`
+		Size     string   `json:"size,omitempty"`
+		Error    string   `json:"error,omitempty"`
+	}
+	out := []rangeInfo{}
+	for _, in := range strings.Split(r.URL.Query().Get("r"), ",") {
+		in = strings.TrimSpace(in)
+		if in == "" || len(out) >= 100 {
+			continue
+		}
+		rg, ok, err := iprange.Parse(strings.TrimSpace(strings.TrimPrefix(in, "!")))
+		switch {
+		case !ok:
+			continue
+		case err != nil:
+			out = append(out, rangeInfo{Input: in, Error: err.Error()})
+		default:
+			ri := rangeInfo{Input: in, Range: rg.String(), Size: rg.SizeText()}
+			for _, pf := range rg.Prefixes() {
+				ri.Prefixes = append(ri.Prefixes, pf.String())
+			}
+			out = append(out, ri)
+		}
+	}
+	writeJSON(w, http.StatusOK, out)
+	return nil
+}
+
 func (s *Server) catalogGrants(w http.ResponseWriter, r *http.Request, p *auth.Principal) error {
 	roles := map[string][]string{}
 	for name, gs := range auth.RoleTemplates {