chore(ci): Enforce strict pipeline failures and remove suppressed errors

Overview

This Merge Request improves CI/CD pipeline reliability and failure handling for the ASR backend project.

Changes Made

• Updated GitLab CI pipeline configuration

• Fixed pipeline status reporting to correctly show:

  • PASSED when all mandatory jobs succeed
  • FAILED when any mandatory job fails

• Removed incorrect warning-only behavior for failed jobs

• Added stricter failure propagation using set -e

• Enforced minimum 95% test coverage using --cov-fail-under=95

• Improved validation flow for:

  • linting
  • formatting
  • type checking
  • testing

• Added safer CI handling for pyupgrade and validation scripts

• Improved pipeline consistency and reliability across all stages

Expected Outcome

• Pipelines no longer show “Passed with warnings” for actual failures
• Any failed mandatory stage now correctly fails the pipeline
• CI validation flow is stricter and more production-safe

*Closes #30 (closed)