feat(ci): separate Failsafe integration tests, merge JaCoCo execution reports, and add Prometheus/Grafana monitoring

[podlLev]

Overview

This PR decouples unit and integration test execution using the Maven Failsafe plugin for Testcontainers-backed suites, configures dual-agent JaCoCo report merging for complete code coverage tracking, updates CI build phases, and introduces Prometheus and Grafana configurations for application metrics monitoring.

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Key Changes

• Build & Testing Lifecycle (Failsafe & JaCoCo):

  • Failsafe Separation: Isolated heavy Testcontainers-backed tests into a dedicated Maven Failsafe integration test phase (*IT naming convention), separating quick unit tests (mvn test) from containerized integration runs (mvn verify).
  • Coverage Report Merging: Configured build settings to run unit and integration tests under distinct JaCoCo Java agents and aggregate both execution data streams into a unified coverage report.

• Continuous Integration & Documentation:

  • CI Pipeline Execution: Updated GitHub Actions workflow steps to execute mvn verify instead of mvn test and added step outputs to publish Failsafe integration test reports alongside Surefire results.
  • Documentation: Updated README.md to clearly detail test lifecycle usage (mvn test vs. mvn verify).

• Metrics & Monitoring Infrastructure:

  • Prometheus & Grafana Setup: Added Prometheus scraper configurations, Grafana dashboard JSON models, and application cache metric exporters to monitor backend runtime performance and cache hits/misses.