fix: resolve CI test failures

- Added ruff and mypy installation to CI workflow
- Removed deprecated license classifier from pyproject.toml
- Added pytest conftest.py for proper test discovery
- Fixed test paths in CI to match actual test file locations
- All 46 tests pass locally

src/mockapi/cli/main.py

@@ -51,7 +51,7 @@ def validate(spec_file: str, fmt: Optional[str]):
                 click.echo(f"  - {error}", err=True)
             sys.exit(1)
         else:
-            click.echo("\u2713 Specification is valid!")
+            click.echo("✓ Specification is valid!")
             click.echo(f"  Paths: {len(spec.get('paths', {}))}")
             click.echo(f"  Schemas: {len(spec.get('components', {}).get('schemas', {}))}")