ci: integrate frontend tests into Maven build + Docker

- Add exec-maven-plugin to pom.xml with 3 npm executions:
  * npm-install (initialize phase)
  * frontend-build (generate-resources phase)
  * frontend-test (test phase)
- Add skipFrontend and skipFrontendTests Maven properties
- Dockerfile now runs npm test in frontend stage
- Dockerfile removes -DskipTests and passes -DskipFrontend=true
  to the Maven stage (frontend already built in its own stage)

pom.xml

@@ -15,6 +15,10 @@
     <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
     <quarkus.platform.version>3.19.2</quarkus.platform.version>
     <quarkus.platform.group-id>io.quarkus.platform</quarkus.platform.group-id>
+    <!-- Set to true to skip all frontend npm tasks (install/build/test) -->
+    <skipFrontend>false</skipFrontend>
+    <!-- Set to true to skip only frontend tests (backend tests still run) -->
+    <skipFrontendTests>false</skipFrontendTests>
   </properties>
 
   <dependencyManagement>
@@ -97,6 +101,55 @@
           </execution>
         </executions>
       </plugin>
+      <!-- Run frontend npm tasks during the Maven lifecycle -->
+      <plugin>
+        <groupId>org.codehaus.mojo</groupId>
+        <artifactId>exec-maven-plugin</artifactId>
+        <version>3.5.0</version>
+        <executions>
+          <execution>
+            <id>npm-install</id>
+            <phase>initialize</phase>
+            <goals><goal>exec</goal></goals>
+            <configuration>
+              <workingDirectory>frontend</workingDirectory>
+              <executable>npm</executable>
+              <arguments>
+                <argument>ci</argument>
+                <argument>--prefer-offline</argument>
+              </arguments>
+              <skip>${skipFrontend}</skip>
+            </configuration>
+          </execution>
+          <execution>
+            <id>frontend-build</id>
+            <phase>generate-resources</phase>
+            <goals><goal>exec</goal></goals>
+            <configuration>
+              <workingDirectory>frontend</workingDirectory>
+              <executable>npm</executable>
+              <arguments>
+                <argument>run</argument>
+                <argument>build</argument>
+              </arguments>
+              <skip>${skipFrontend}</skip>
+            </configuration>
+          </execution>
+          <execution>
+            <id>frontend-test</id>
+            <phase>test</phase>
+            <goals><goal>exec</goal></goals>
+            <configuration>
+              <workingDirectory>frontend</workingDirectory>
+              <executable>npm</executable>
+              <arguments>
+                <argument>test</argument>
+              </arguments>
+              <skip>${skipFrontendTests}</skip>
+            </configuration>
+          </execution>
+        </executions>
+      </plugin>
     </plugins>
   </build>
 </project>