test(http): tighten SSL-failure assertion + null-guard WireMock teardown

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

cameleer-server-app/src/test/java/com/cameleer/server/app/http/ApacheOutboundHttpClientFactoryIT.java

@@ -38,7 +38,7 @@ class ApacheOutboundHttpClientFactoryIT {
 
     @AfterEach
     void tearDown() {
-        wm.stop();
+        if (wm != null) wm.stop();
     }
 
     @Test
@@ -55,7 +55,7 @@ class ApacheOutboundHttpClientFactoryIT {
     void systemDefaultRejectsSelfSignedCert() {
         CloseableHttpClient client = factory.clientFor(OutboundHttpRequestContext.systemDefault());
         assertThatThrownBy(() -> client.execute(new HttpGet("https://localhost:" + wm.httpsPort() + "/ping")))
-                .hasMessageContaining("PKIX");
+                .isInstanceOfAny(javax.net.ssl.SSLException.class, javax.net.ssl.SSLHandshakeException.class);
     }
 
     @Test