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>

server/src/router/v1/auth/trustDevice.helper.js

@@ -0,0 +1,46 @@
+// ── Shared trusted-device establishment ────────────────────────────────────
+//
+// One place that mints + persists a trusted device, enforces the per-user cap
+// (no silent pruning), and audit-logs it. Reused by every path that can create a
+// trust: web /auth/login/totp, mobile /auth/mobile/login, and the authenticated
+// self-service POST /auth/me/trusted-devices (the "revoke one, then retry" path
+// after a cap-reached prompt).
+//
+// The caller decides how the returned trust token reaches the client: the web
+// paths set the httpOnly rg_trust cookie (setTrustCookie); native paths return the
+// token in the JSON body for EncryptedSharedPreferences. This helper never touches
+// res, so it stays surface-agnostic.
+
+const trustedDevices = require('../../../model/trustedDevices/trustedDevices.model')
+const activity = require('../../../model/activity/activity.model')
+const sessionService = require('../../../auth/session.service')
+
+const log = require('../../../utils/logger')('trusted-device')
+
+// Attempt to trust the current device for `user`. Returns:
+//   { ok: true, trustToken }                     — trusted; caller delivers the token
+//   { ok: false, capReached: true, devices }     — at the cap; caller prompts to revoke
+// `platform` is 'web' | 'mobile'; `deviceName` is the optional friendly label.
+async function establishTrust(req, user, { platform = 'web', deviceName = null } = {}) {
+  if (await sessionService.trustDeviceCapReached(user.id)) {
+    const devices = await trustedDevices.listActiveForUser(user.id)
+    log.info('trust refused — device cap reached', { userId: user.id, platform })
+    return { ok: false, capReached: true, devices }
+  }
+  const meta = sessionService.sessionMeta(req)
+  const out = sessionService.mintTrustToken(meta)
+  await trustedDevices.store({
+    userId: user.id,
+    tokenHash: out.trustHash,
+    platform,
+    deviceName,
+    deviceHash: out.deviceHash,
+    userAgent: out.userAgent,
+    expiresAt: out.expiresAt,
+  })
+  await activity.log({ req, userId: user.id, action: 'account.trusted_device.add', detail: { platform } })
+  log.info('device trusted', { userId: user.id, platform })
+  return { ok: true, trustToken: out.trustToken }
+}
+
+module.exports = { establishTrust }