Fix missing dependency version during mvn verify, put shared example dependencies to parent

[mvlcak]

This PR fixes why mvn clean package failed with missing dependency version for one of the examples. Each example module independently declared its own spring-ai.version and spring-boot parent, leading to version drift across examples This caused build failures and made version updates error-prone.

Changes

examples/pom.xml (examples-parent)

• Added <parent> pointing to spring-ai-agent-utils-parent so spring-ai.version is now inherited from the root pom
• Bumped version to 0.2.0-SNAPSHOT
• Added spring-boot.version property (4.0.6)
• Added <dependencyManagement> importing spring-boot-dependencies and spring-ai-bom BOMs — replaces spring-boot-starter-parent as the source of dependency versions
• Added <build><plugin> for spring-boot-maven-plugin
• Removed <repositories> — inherited from root

Result

Spring AI and Spring Boot versions are now defined in one place.
Bumping a version requires changing a single property.