fix: use Jakarta EE packages for Spring Boot 4 compatibility

Revert useSpringBoot3 flag back to true. Despite the name, this flag is needed for Spring Boot 4 because it generates code using Jakarta EE packages (jakarta.*) instead of the deprecated Java EE packages (javax.*).

Spring Boot 3+ migrated from javax.* to jakarta.* packages, and Spring Boot 4 continues using jakarta.* packages. Setting useSpringBoot3 to false incorrectly generates code with javax.* imports which don't exist in modern Java.

Fixes compilation errors with:
- javax.validation -> jakarta.validation
- javax.annotation -> jakarta.annotation
- javax.servlet -> jakarta.servlet

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

Author: klagrida

backend/pom.xml

@@ -100,7 +100,7 @@
                     <modelPackage>com.example.taskmanager.generated.model</modelPackage>
                     <configOptions>
                         <interfaceOnly>true</interfaceOnly>
-                        <useSpringBoot3>false</useSpringBoot3>
+                        <useSpringBoot3>true</useSpringBoot3>
                         <documentationProvider>springdoc</documentationProvider>
                         <useTags>true</useTags>
                         <delegatePattern>false</delegatePattern>

openapitools.json

@@ -13,7 +13,7 @@
         "modelPackage": "com.example.taskmanager.model",
         "additionalProperties": {
           "interfaceOnly": "true",
-          "useSpringBoot3": "false",
+          "useSpringBoot3": "true",
           "documentationProvider": "springdoc",
           "useTags": "true",
           "delegatePattern": "false",