Harden admin login: RBAC-safe controls, 2FA, bot-scoring, rate limits (#9)

Adds a layered set of protections around the admin login and the app edge.

Trust proxy (server/src/utils/trustProxy.js)
- Configurable via TRUST_PROXY; pin to the newt agent ("ptero") LAN IP so
  X-Forwarded-For is trusted ONLY from that peer. A blanket "true" is
  rejected (coerced to 1) to prevent XFF spoofing that would dodge every
  IP-based control. DEBUG_TRUST_PROXY logs peer/XFF/req.ip to re-verify the
  proxy IP without a redeploy. Documents the Omada static-reservation
  assumption.

Login throttling (server/src/middleware/loginProtection.js, rateLimit.js)
- express-slow-down progressive delay + the existing hard rate cap + a
  separate per-IP exponential backoff that persists across the rate window.
  All failures return one generic message (no user/pass disclosure).

Honeypot (login form + auth.controller)
- Hidden, plausibly-named field ("company"); a filled value fails
  generically and is scored as an unambiguous bot.

Optional per-user TOTP 2FA (speakeasy/qrcode)
- totp_secret/totp_enabled columns (+ idempotent migration). Self-service
  Account page: enroll via QR, confirm a code to enable, code-gated disable.
- Login is two-step for enrolled users: after the password, a short-lived
  signed challenge (stage:'totp', not a session) is required before the
  real session is issued.

Bot / scanner scoring + IP ban (server/src/middleware/botScore.js)
- Weighted CMS-scanner paths (this app uses none). Junk paths 404 FIRST,
  unconditionally — independent of score/ban state, so a scanner rotating
  through fresh Cloudflare IPs gets no free pass. /wp-admin/install.php is
  the top-weighted near-1-hit ban (worst offender in prod logs). Per-IP
  score with quiet-period decay temp-bans an IP from ALL routes once past a
  (deliberately low) threshold, to protect /admin from credential stuffing.
  Failed logins and honeypot hits feed the same score.
- Periodic sweep evicts stale, unbanned, quiet entries so the in-memory
  store can't grow unbounded; the interval is unref'd and cleared on
  graceful shutdown.

Tests: node --test suite (40) covering trust-proxy parsing + live req.ip
(incl. pinned-IP), rate limiter + exponential backoff, honeypot rejection,
TOTP verify (enabled/disabled) + challenge-isn't-a-session, bot-score
threshold/decay/ban + junk-404-independence + install.php + store sweep.

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

client/src/routes/admin/AdminLayout.jsx

@@ -12,6 +12,7 @@ const NAV = [
   { to: '/admin/settings', label: 'Settings' },
   { to: '/admin/activity', label: 'Activity' },
   { to: '/admin/users', label: 'Users' },
+  { to: '/admin/account', label: 'Account' },
 ]
 
 const TITLES = {
@@ -22,6 +23,7 @@ const TITLES = {
   '/admin/settings': 'Site Settings',
   '/admin/activity': 'Activity Log',
   '/admin/users': 'Users',
+  '/admin/account': 'Account Security',
 }
 
 const navBtnBase = {