[Testing] Test coverage >80%: Add comprehensive test suite for all components

[OneByJorah]

Test Coverage Checklist

• Audit current test coverage:
  • - basic health checks only
  • - component health checks
  • No unit tests for scripts
  • No integration tests for docker-compose stack
  • No contract tests for APIs (SearXNG, Camofox, Honcho, Obsidian)
• Add test infrastructure:
  • Create test framework for shell scripts (bats or shunit2)
  • Add unit tests for all shell scripts ()
  • Add integration tests for docker-compose stack (bats + docker)
  • Add contract tests for service APIs
  • Add browser-search npm tests (jest/vitest)
• Configure codecov/coveralls integration
• Add test coverage reporting to CI
• Enforce >80% coverage gate in CI
• Add mutation testing for critical paths