feat(auth): trusted devices, recovery codes, and admin MFA management

Add opt-in "Trust this device" so a browser/app skips the TOTP step (never
the password) for 30 days, single-use bcrypt recovery codes as a 2FA-lockout
fallback, and admin trusted-device/MFA-reset management — backend, web UI,
OpenAPI spec, and tests.

- Schema: trusted_devices (sha256 token hash, looked up by unique index) and
  recovery_codes (bcrypt, single-use). Both additive/idempotent.
- Session service: trust-token mint/hash/resolve + cap helpers; new rg_trust
  httpOnly cookie (survives logout, revoked on untrust/password change/reset/
  TOTP disable). JWTs stay stateless — trust is a server-side row, not a claim.
- Web + mobile login accept a trusted-device token / recovery code; login/totp
  gains trustDevice + recoveryCode. Cap of 10/user with NO silent pruning — an
  over-cap trust returns 409/trustLimitReached and the client prompts to revoke.
- Self-service /auth/me/trusted-devices* + recovery-codes*; admin
  /admin/users/:id/trusted-devices* + /mfa/reset. All actions audit-logged.
- Client: "Trust this device" + recovery-code login options, one-time recovery
  code display, Trusted Devices + Recovery Codes account panels, a TOTP-styled
  revoke-to-continue cap modal, and admin per-user security controls.
- OpenAPI regenerated; 33 new server tests (all suites green).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

client/src/routes/admin/views/AccountAdmin.jsx

@@ -1,6 +1,9 @@
 import { useCallback, useEffect, useState } from 'react'
 import { Loading, ErrorState } from '../../../components/PageState.jsx'
 import ProviderIcon from '../../../components/ProviderIcon.jsx'
+import RecoveryCodesDisplay from '../../../components/security/RecoveryCodesDisplay.jsx'
+import TrustedDevicesPanel from '../../../components/security/TrustedDevicesPanel.jsx'
+import RecoveryCodesPanel from '../../../components/security/RecoveryCodesPanel.jsx'
 import { api } from '../../../api/client.js'
 
 // Link/unlink external SSO identities to this account. Linking redirects through
@@ -127,6 +130,7 @@ export default function AccountAdmin() {
   const [code, setCode] = useState('')
   const [busy, setBusy] = useState(false)
   const [msg, setMsg] = useState('')
+  const [newCodes, setNewCodes] = useState(null) // one-time recovery codes shown after enabling
 
   async function load() {
     try {
@@ -164,9 +168,10 @@ export default function AccountAdmin() {
     setMsg('')
     setError('')
     try {
-      await api.admin.totpEnable(code.trim())
+      const res = await api.admin.totpEnable(code.trim())
       setSetup(null)
       setCode('')
+      setNewCodes(res?.recoveryCodes || null)
       setMsg('Two-factor authentication is now enabled.')
       await load()
     } catch (err) {
@@ -302,6 +307,21 @@ export default function AccountAdmin() {
       {msg && <p className="sans" style={{ marginTop: 16, color: '#7fd0a4', fontSize: '0.86rem' }}>{msg}</p>}
       {error && <p className="sans" style={{ marginTop: 16, color: '#d98b84', fontSize: '0.86rem' }}>{error}</p>}
 
+      {/* One-time recovery codes shown right after enabling 2FA. */}
+      {newCodes && (
+        <div style={{ marginTop: 20 }}>
+          <RecoveryCodesDisplay codes={newCodes} onDone={() => setNewCodes(null)} />
+        </div>
+      )}
+
+      {/* Trusted devices + recovery-code management, only relevant with 2FA on. */}
+      {enabled && (
+        <>
+          <TrustedDevicesPanel />
+          <RecoveryCodesPanel hasPassword={account?.has_password !== false} />
+        </>
+      )}
+
       <LinkedAccounts />
     </section>
   )