fix(security): harden PoW XSS, email header injection and UptimeKuma log redaction

pkg/mail/mail_test.go

@@ -90,3 +90,23 @@ func TestSendMailMock(t *testing.T) {
 		t.Errorf("failed to send mail: %v", err)
 	}
 }
+
+func TestSanitizeHeaderValue(t *testing.T) {
+	tests := []struct {
+		name  string
+		input string
+		want  string
+	}{
+		{"plain", "System Notification", "System Notification"},
+		{"crlf stripped", "alert\r\nBcc: attacker@example.com", "alertBcc: attacker@example.com"},
+		{"cr stripped", "a\rb", "ab"},
+		{"lf stripped", "a\nb", "ab"},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := sanitizeHeaderValue(tt.input); got != tt.want {
+				t.Errorf("sanitizeHeaderValue(%q) = %q, want %q", tt.input, got, tt.want)
+			}
+		})
+	}
+}