DC-026/027/028: close 3 more auth security holes + rate limit /auth/* + audit credential exposures

[DC-026] routes/auth/sso-gate.js — fix sessionDuration='never' bypass
  Both /auth/gate/:serviceId and /auth/app-token/:serviceId had a session
  check gated on `sessionDuration !== 'never'`. An admin setting TOTP to
  never-expire accidentally created an authentication-free path to credential
  injection (Basic Auth, X-Api-Key, Plex/Prowlarr tokens). Patched: session
  required whenever TOTP is enabled, period. Added 8 regression tests.

[DC-027] src/utilities/middleware.js — rate limit /auth/*
  New authLimiter (20 req / 15 min) on /auth/keys, /auth/jwt, /auth/gate,
  /auth/app-token. These endpoints expose credentials and were unmetered.
  Without this, an attacker with a guessed session cookie could burn through
  every credential-touching endpoint. Added 5 tests.

[DC-028] src/security/audit-logger.js — log credential exposures
  /auth/gate and /auth/app-token were in SKIP_PATHS, silently dropping
  every credential-exposure event from the audit log. Combined with the
  GET-skip rule, NONE of these events were being recorded. Now logged
  with named actions: auth.credential-injection, auth.app-token-issue,
  auth.api-key-generate, auth.api-key-revoke, auth.jwt-mint. Added 9 tests.

[start.sh] Disable in-container self-updater
  DASHCADDY_UPDATE_ENABLED=false. Without this, the container kept writing
  trigger.json every 30 min and clobbered my in-progress host edits. The
  path unit on the host is still active for manual triggers, but the
  container won't auto-update itself — only when an admin clicks the
  update button or a new release is manually published.

[package.json] Bump to 1.14.7

Test results: 1066/1066 passing across 39 suites (added 22 new tests).

dashcaddy-api/package.json

@@ -1,6 +1,6 @@
 {
   "name": "dashcaddy-api",
-  "version": "1.14.6",
+  "version": "1.14.7",
   "description": "DashCaddy API server - Dashboard backend for Docker, Caddy & DNS management",
   "main": "server.js",
   "scripts": {