Hardening Maestro CI: Resolve SpotBugs violations and enable static analysis

[developertogo]

Fixes #164

Pull Request type

• Bugfix
• Feature
• Refactoring (no functional changes, no api changes)
• Build related changes (Please run ./gradlew build --write-locks to refresh dependencies)
• Other (please describe):

NOTE: Please remember to run ./gradlew spotlessApply to fix any format violations.

Changes in this PR

Description

This PR resolves existing SpotBugs violations across the entire Maestro codebase—including maestro-engine, maestro-queue, maestro-common, maestro-flow, and maestro-server — enabling the SpotBugs plugin to enforce static analysis in the CI pipeline [issue #164 - Enable spotbugs plugin]. The changes focus on improving thread safety, ensuring consistent boolean evaluation, and securing randomness in concurrent contexts.

Changes Made

• SpotBugs Resolution: Addressed representation exposure (EI_EXPOSE_REP/2) and suspicious reference comparisons (RC_REF_COMPARISON_BOOLEAN) across DAO layers.
• Null-Safe Logic: Migrated boolean flag evaluations in MaestroWorkflowDao to use null-safe Boolean.TRUE.equals() patterns.
• Thread Safety: Applied the volatile keyword to the running state in MaestroQueueWorker to ensure cross-thread visibility.
• Secure Randomness: Replaced Math.random() with ThreadLocalRandom in MaestroQueueWorker to optimize performance and safety in high-concurrency queue processing.
• Warning Suppression: Applied targeted @SuppressFBWarnings for intentional design patterns (e.g., catching NullPointerException for idempotency and intentional ignored return values).

Test Verification

Automated Tests

• Validated all changes by running the full static analysis suite:

  ./gradlew spotbugsMain checkstyleMain pmdMain

• Verified project build and unit test integrity:

  ./gradlew clean check test assemble