fix(phase3): skip templateless domains in scheduler; block CGNAT range in webhook SSRF guard

Domains imported without a template (TemplateID == nil) are a valid,
unconfigured state, not a failure — RunOnce now skips them before
calling checkDomain instead of letting LoadDomain's "no template" error
turn into StatusError and a spammy unknown->error notification.

isBlockedIP now also rejects 100.64.0.0/10 (RFC 6598 carrier-grade
NAT), which net.IP.IsPrivate() does not cover, closing an SSRF gap in
the webhook destination guard (both the pre-request check and the
per-dial check use isBlockedIP).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01BwxdSt4reTm7Dj1oxRvpP3

internal/notify/notify_test.go

@@ -3,6 +3,7 @@ package notify
 import (
 	"context"
 	"encoding/json"
+	"net"
 	"net/http"
 	"net/http/httptest"
 	"strings"
@@ -195,6 +196,31 @@ func TestDialControlBlocksActualConnectingAddress(t *testing.T) {
 	}
 }
 
+func TestIsBlockedIPCGNATRange(t *testing.T) {
+	cases := []struct {
+		name    string
+		ip      string
+		blocked bool
+	}{
+		{"cgnat start", "100.64.0.1", true},
+		{"cgnat end", "100.127.255.255", true},
+		{"just below cgnat", "100.63.255.255", false},
+		{"just above cgnat", "100.128.0.0", false},
+	}
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			ip := net.ParseIP(tc.ip)
+			if ip == nil {
+				t.Fatalf("failed to parse %q", tc.ip)
+			}
+			got := isBlockedIP(ip)
+			if got != tc.blocked {
+				t.Fatalf("isBlockedIP(%q) = %v, want %v", tc.ip, got, tc.blocked)
+			}
+		})
+	}
+}
+
 func TestDialControlAllowsEverythingWhenAllowPrivate(t *testing.T) {
 	control := dialControl(true)
 	if err := control("tcp", "127.0.0.1:80", nil); err != nil {