Remove JpaUtils and refactor repository access

Eliminated the static `JpaUtils` utility and transitioned to explicit repository management for improved modularity and testability. Updated `GuildService`, `TaskManagerImpl`, and related classes to use dependency-injected repositories. Simplified configuration by aligning repository definitions with existing service patterns and ensuring proper session handling through `SessionManager`. Verified that all affected components function as expected after refactoring.

pom.xml

@@ -18,6 +18,7 @@
         <maven.compiler.source>25</maven.compiler.source>
         <maven.compiler.target>25</maven.compiler.target>
         <mockito.version>5.23.0</mockito.version>
+        <testcontainers.version>2.0.5</testcontainers.version>
     </properties>
 
     <build>
@@ -273,6 +274,18 @@
             <version>${mockito.version}</version>
             <scope>test</scope>
         </dependency>
+        <dependency>
+            <groupId>org.testcontainers</groupId>
+            <artifactId>testcontainers-junit-jupiter</artifactId>
+            <version>${testcontainers.version}</version>
+            <scope>test</scope>
+        </dependency>
+        <dependency>
+            <groupId>org.testcontainers</groupId>
+            <artifactId>testcontainers-mysql</artifactId>
+            <version>${testcontainers.version}</version>
+            <scope>test</scope>
+        </dependency>
     </dependencies>
 
 </project>