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/search/SearchControllerTest.java

@@ -1,5 +1,7 @@
 package com.vaessl.app.search;
 
+import static com.vaessl.app.Mockdata.MOCK_PASS;
+import static com.vaessl.app.Mockdata.MOCK_USER;
 import static com.vaessl.app.connection.Endpoint.*;
 import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.*;
 import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.*;
@@ -24,10 +26,6 @@ class SearchControllerTest {
     @Autowired
     MockMvc mockMvc;
 
-    private static final String TEST_USER = "admin";
-
-    private static final String TEST_PASS = "pw";
-
     private static final String QUERY_ALL_ITEMS = HOMEBOX_QUERY_ALL_ITEMS.getValue();
 
     private static final String LOGIN_PATH = LOGIN.getValue();
@@ -138,7 +136,7 @@ class SearchControllerTest {
                     "serviceType": "%s",
                     "username": "%s"
                 }
-                """.formatted(wm.getHttpBaseUrl(), serviceType, TEST_USER);
+                """.formatted(wm.getHttpBaseUrl(), serviceType, MOCK_USER);
     }
 
     private String connectionRequestBody(WireMockRuntimeInfo wm) {
@@ -149,6 +147,6 @@ class SearchControllerTest {
                     "username": "%s",
                     "password": "%s"
                 }
-                """.formatted(wm.getHttpBaseUrl(), TEST_USER, TEST_PASS);
+                """.formatted(wm.getHttpBaseUrl(), MOCK_USER, MOCK_PASS);
     }
 }