Add Migadu domain admin with shared lists, compaction, and safer apply.

Build the Go API and React UI for managing domain denylist/allowlist/recipient
deny and spam settings, plus shared lists that import/apply across domains with
wildcard compaction, entry verification, and Migadu-friendly list encoding
(including per-domain recipient filtering and rejection bisect on apply).

internal/config/config_test.go

@@ -0,0 +1,25 @@
+package config
+
+import (
+	"net"
+	"testing"
+)
+
+func TestIsTrustedProxy(t *testing.T) {
+	cfg := &Config{}
+	networks, err := parseCIDRs("10.0.0.0/8,127.0.0.1")
+	if err != nil {
+		t.Fatal(err)
+	}
+	cfg.TrustedProxies = networks
+
+	if !cfg.IsTrustedProxy(net.ParseIP("10.1.2.3")) {
+		t.Fatal("expected 10.1.2.3 trusted")
+	}
+	if !cfg.IsTrustedProxy(net.ParseIP("127.0.0.1")) {
+		t.Fatal("expected 127.0.0.1 trusted")
+	}
+	if cfg.IsTrustedProxy(net.ParseIP("192.168.1.1")) {
+		t.Fatal("expected 192.168.1.1 untrusted")
+	}
+}