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>

openapi.yaml

@@ -550,6 +550,17 @@ paths:
       tags: [Auth]
       security:
         - bearerAuth: []
+      requestBody:
+        required: true
+        content:
+          application/json:
+            schema:
+              type: object
+              required: [password]
+              properties:
+                password:
+                  type: string
+                  description: Current account password (required to prevent session-theft escalation).
       responses:
         "200":
           description: TOTP secret generated.