refactor: consolidate test mock constants into shared Mockdata class

Moved Mockdata from the connection package to the root test package and
extended it with MOCK_USER, MOCK_PASS, MOCK_TITLE, and MOCK_DESCRIPTION
so all test modules share a single source of truth. Removed duplicate
inline constants from ConnectionControllerTest, HomeboxIntegrationTest,
and SearchControllerTest.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/src/test/java/com/vaessl/app/connection/HomeboxIntegrationTest.java

@@ -1,5 +1,6 @@
 package com.vaessl.app.connection;
 
+import static com.vaessl.app.Mockdata.*;
 import org.junit.jupiter.api.Test;
 import org.springframework.beans.factory.annotation.Autowired;
 import org.springframework.boot.resttestclient.TestRestTemplate;
@@ -41,9 +42,6 @@ class HomeboxIntegrationTest {
             }
                 """;
 
-    private static final String TEST_USER = "admin";
-    private static final String TEST_PASS = "pw";
-
     /**
      * Returns Token and status code OK when login is successful.
      * 
@@ -139,7 +137,7 @@ class HomeboxIntegrationTest {
     @Test
     void shouldReturnWrongServiceTypeException(WireMockRuntimeInfo wm) {
         ConnectionRequest wrongServiceTypeReq = new ConnectionRequest(wm.getHttpBaseUrl(),
-                "wrong-service-type", TEST_USER, TEST_PASS, false);
+                "wrong-service-type", MOCK_USER, MOCK_PASS, false);
 
         ResponseEntity<String> response =
                 restTemplate.postForEntity(LOGIN.getValue(), wrongServiceTypeReq, String.class);
@@ -182,7 +180,7 @@ class HomeboxIntegrationTest {
     @Test
     void shouldReturnEmptyCredentialsExceptionWhenCredsAreMissing(WireMockRuntimeInfo wm) {
         ConnectionRequest missingCredentials = new ConnectionRequest(wm.getHttpBaseUrl(),
-                HOMEBOX.getValue(), TEST_USER, null, false);
+                HOMEBOX.getValue(), MOCK_USER, null, false);
 
         ResponseEntity<String> response =
                 restTemplate.postForEntity(LOGIN.getValue(), missingCredentials, String.class);
@@ -198,7 +196,7 @@ class HomeboxIntegrationTest {
      * @return a mock api connection request.
      */
     private ConnectionRequest connectionRequest(WireMockRuntimeInfo wm) {
-        return new ConnectionRequest(wm.getHttpBaseUrl(), HOMEBOX.getValue(), TEST_USER, TEST_PASS,
+        return new ConnectionRequest(wm.getHttpBaseUrl(), HOMEBOX.getValue(), MOCK_USER, MOCK_PASS,
                 null);
     }
 }