Fix SEC-01: require password for TOTP enroll

- REST handleTOTPEnroll now requires password field in request body
- gRPC EnrollTOTP updated with password field in proto message
- Both handlers check lockout status and record failures on bad password
- Updated Go, Python, and Rust client libraries to pass password
- Updated OpenAPI specs with new requestBody schema
- Added TestTOTPEnrollRequiresPassword with no-password, wrong-password,
  and correct-password sub-tests

Security: TOTP enrollment now requires the current password to prevent
session-theft escalation to persistent account takeover. Lockout and
failure recording use the same Argon2id constant-time path as login.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

clients/go/client_test.go

@@ -275,7 +275,7 @@ func TestEnrollTOTP(t *testing.T) {
 	}))
 	defer srv.Close()
 	c := newTestClient(t, srv.URL)
-	resp, err := c.EnrollTOTP()
+	resp, err := c.EnrollTOTP("testpass123")
 	if err != nil {
 		t.Fatalf("EnrollTOTP: %v", err)
 	}