🧪 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>

pkg/user/user.go

@@ -39,6 +39,10 @@ type AuthService interface {
 	GenerateJWT(ctx context.Context, user *User) (string, error)
 	ValidateJWT(ctx context.Context, token string) (*User, error)
 	AdminAuthenticate(ctx context.Context, masterPassword string) (*User, error)
+	AddJWTSecret(secret string, isPrimary bool, expiresIn time.Duration)
+	RotateJWTSecret(newSecret string)
+	GetJWTSecretByIndex(index int) (string, bool)
+	ResetJWTSecrets() // Reset JWT secrets to initial state for test cleanup
 }
 
 // UserManager defines interface for user management operations