🧪 test: add JWT secret rotation BDD scenarios and step implementations (#12)

✨ merge: implement JWT secret rotation with BDD scenario isolation

- Implement JWT secret rotation mechanism (closes #8)
- Add per-scenario state isolation for BDD tests (closes #14)
- Validate password reset workflow via BDD tests (closes #7)
- Fix port conflicts in test validation
- Add state tracer for debugging test execution
- Document BDD isolation strategies in ADR 0025
- Fix PostgreSQL configuration environment variables

Generated by Mistral Vibe.
Co-Authored-By: Mistral Vibe <vibe@mistral.ai>
Co-authored-by: Gabriel Radureau <arcodange@gmail.com>
Co-committed-by: Gabriel Radureau <arcodange@gmail.com>

features/health/health.feature

@@ -0,0 +1,10 @@
+# features/health.feature
+@health @smoke @critical
+Feature: Health Endpoint
+  The health endpoint should indicate server status
+
+  @basic @critical
+  Scenario: Health check returns healthy status
+    Given the server is running
+    When I request the health endpoint
+    Then the response should be "{\"status\":\"healthy\"}"