Add comprehensive E2E tests for materia CLI

- Add pytest and pytest-cov for testing
- Add niquests for modern HTTP/2 support (keep requests for hcloud compatibility)
- Create 13 E2E tests covering CLI, workers, pipelines, and secrets (71% coverage)
- Fix Pulumi ESC environment path (beanflows/prod) and secret key names
- Update GitLab CI to run CLI tests with coverage reporting

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/materia/secrets.py

@@ -10,13 +10,13 @@ def _load_environment() -> dict[str, str]:
     """Load secrets from Pulumi ESC environment."""
     try:
         result = subprocess.run(
-            ["esc", "env", "open", "prod", "--format", "json"],
+            ["esc", "env", "open", "beanflows/prod", "--format", "json"],
             capture_output=True,
             text=True,
             check=True,
         )
         data = json.loads(result.stdout)
-        return data.get("values", {})
+        return data.get("environmentVariables", {})
     except subprocess.CalledProcessError as e:
         raise RuntimeError(f"Failed to load ESC environment: {e.stderr}")
     except FileNotFoundError: