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/lists/validate_test.go

@@ -0,0 +1,45 @@
+package lists
+
+import "testing"
+
+func TestValidateEntries(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name    string
+		entries []string
+		wantN   int
+	}{
+		{name: "empty list", entries: nil, wantN: 0},
+		{name: "valid user", entries: []string{"user@example.com"}, wantN: 0},
+		{name: "valid star domain", entries: []string{"*@example.com"}, wantN: 0},
+		{name: "valid suffix glob", entries: []string{"*@*.shop", "*@*.ac.in"}, wantN: 0},
+		{name: "valid plus addressing", entries: []string{"a.b+c@mail-host.co.uk"}, wantN: 0},
+		{name: "repair then valid", entries: []string{"*vsa.instalily.ai"}, wantN: 0},
+		{name: "missing at", entries: []string{"not-an-email"}, wantN: 1},
+		{name: "bare domain", entries: []string{"example.com"}, wantN: 1},
+		{name: "spaces", entries: []string{"user @example.com"}, wantN: 1},
+		{name: "bad domain", entries: []string{"user@-example.com"}, wantN: 1},
+		{name: "single label domain", entries: []string{"*@localhost"}, wantN: 1},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+			got := ValidateEntries(tt.entries)
+			if len(got) != tt.wantN {
+				t.Fatalf("ValidateEntries() issues=%v want %d", got, tt.wantN)
+			}
+		})
+	}
+}
+
+func TestValidateEntryReasons(t *testing.T) {
+	t.Parallel()
+	if got := ValidateEntry(""); got == "" {
+		t.Fatal("expected empty reason")
+	}
+	if got := ValidateEntry("lisa@simpsons.com"); got != "" {
+		t.Fatalf("unexpected: %s", got)
+	}
+}