[AURON #1879] Add maven checkstyle plugin

[yew1eb]

Which issue does this PR close?

Closes #1879

Rationale for this change

What changes are included in this PR?

Are there any user-facing changes?

How was this patch tested?

[cxzl25]

I'm not sure why we still need checkstyle? Because we have used spotless-maven-plugin.

auron/pom.xml

Lines 488 to 507 in 3264372

	<artifactId>spotless-maven-plugin</artifactId>
	<version>${spotless.plugin.version}</version>
	<configuration>
	<java>
	<palantirJavaFormat />
	<removeUnusedImports />
	<licenseHeader>
	<file>${maven.multiModuleProjectDirectory}/dev/license-header</file>
	</licenseHeader>
	</java>
	<scala>
	<scalafmt>
	<version>${scalafmtVersion}</version>
	<file>${maven.multiModuleProjectDirectory}/scalafmt.conf</file>
	<scalaMajorVersion>${scalaVersion}</scalaMajorVersion>
	</scalafmt>
	<licenseHeader>
	<file>${maven.multiModuleProjectDirectory}/dev/license-header</file>
	</licenseHeader>
	</scala>

[yew1eb]

add Checkstyle to complement Spotless — while both serve as quality gates, Spotless focuses on format consistency (auto-fixable) and Checkstyle on semantic style rules (readability/maintainability) that Spotless doesn’t address. This dual setup ensures comprehensive code standard enforcement, which is critical for project quality.