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>

internal/server/server_test.go

@@ -519,8 +519,10 @@ func TestTOTPEnrollDoesNotRequireTOTP(t *testing.T) {
 		t.Fatalf("TrackToken: %v", err)
 	}
 
-	// Start enrollment.
-	rr := doRequest(t, handler, "POST", "/v1/auth/totp/enroll", nil, tokenStr)
+	// Start enrollment (password required since SEC-01 fix).
+	rr := doRequest(t, handler, "POST", "/v1/auth/totp/enroll", totpEnrollRequest{
+		Password: "testpass123",
+	}, tokenStr)
 	if rr.Code != http.StatusOK {
 		t.Fatalf("enroll status = %d, want 200; body: %s", rr.Code, rr.Body.String())
 	}
@@ -558,6 +560,61 @@ func TestTOTPEnrollDoesNotRequireTOTP(t *testing.T) {
 	}
 }
 
+// TestTOTPEnrollRequiresPassword verifies that TOTP enrollment (SEC-01)
+// requires the current password.  A stolen session token alone must not be
+// sufficient to add attacker-controlled MFA to the victim's account.
+func TestTOTPEnrollRequiresPassword(t *testing.T) {
+	srv, _, priv, _ := newTestServer(t)
+	acct := createTestHumanAccount(t, srv, "totp-pw-check")
+	handler := srv.Handler()
+
+	tokenStr, claims, err := token.IssueToken(priv, testIssuer, acct.UUID, nil, time.Hour)
+	if err != nil {
+		t.Fatalf("IssueToken: %v", err)
+	}
+	if err := srv.db.TrackToken(claims.JTI, acct.ID, claims.IssuedAt, claims.ExpiresAt); err != nil {
+		t.Fatalf("TrackToken: %v", err)
+	}
+
+	t.Run("no password", func(t *testing.T) {
+		rr := doRequest(t, handler, "POST", "/v1/auth/totp/enroll", totpEnrollRequest{}, tokenStr)
+		if rr.Code != http.StatusBadRequest {
+			t.Errorf("enroll without password: status = %d, want %d; body: %s",
+				rr.Code, http.StatusBadRequest, rr.Body.String())
+		}
+	})
+
+	t.Run("wrong password", func(t *testing.T) {
+		rr := doRequest(t, handler, "POST", "/v1/auth/totp/enroll", totpEnrollRequest{
+			Password: "wrong-password",
+		}, tokenStr)
+		if rr.Code != http.StatusUnauthorized {
+			t.Errorf("enroll with wrong password: status = %d, want %d; body: %s",
+				rr.Code, http.StatusUnauthorized, rr.Body.String())
+		}
+	})
+
+	t.Run("correct password", func(t *testing.T) {
+		rr := doRequest(t, handler, "POST", "/v1/auth/totp/enroll", totpEnrollRequest{
+			Password: "testpass123",
+		}, tokenStr)
+		if rr.Code != http.StatusOK {
+			t.Fatalf("enroll with correct password: status = %d, want 200; body: %s",
+				rr.Code, rr.Body.String())
+		}
+		var resp totpEnrollResponse
+		if err := json.Unmarshal(rr.Body.Bytes(), &resp); err != nil {
+			t.Fatalf("unmarshal: %v", err)
+		}
+		if resp.Secret == "" {
+			t.Error("expected non-empty TOTP secret")
+		}
+		if resp.OTPAuthURI == "" {
+			t.Error("expected non-empty otpauth URI")
+		}
+	})
+}
+
 func TestRenewToken(t *testing.T) {
 	srv, _, priv, _ := newTestServer(t)
 	acct := createTestHumanAccount(t, srv, "renew-user")