fix(uds-auth): keep sessions until manual sign-out; refresh expired UAC tokens by QR (0.3.20)

Users were asked to sign in again every ~30 minutes, even while active.

Session lifetime
- Browser: UDS_SESSION kept its login-time Max-Age and was never re-issued,
  so the cookie vanished 30 min after login. Re-issue it on use (throttled
  by slidingInterval).
- Desktop: remote.mux WS traffic never passed the HTTP auth middleware, so
  the idle TTL never slid. assertPrincipalLive now reports activity and
  slides the session and the account's bridges (throttled).
- New setting sessionIdleTimeoutHours (Settings page + config). Default 0 =
  no automatic sign-out; only a manual sign-out ends a session, so
  conversations and night-time cron are never cut off. 0.5-168 enables an
  idle timeout with the 7-day cap. The TTL is read live.
- Stores support long TTLs: the absolute cap follows the TTL, older 7-day
  sessions are lifted on activity, and expiry timers re-arm instead of
  overflowing setTimeout (~24.8 days).

UAC token check
- Every 2 hours (and 1 min after start) each QR session's token is checked
  against icenterapi. A rejected token is only flagged, never a sign-out.
  Network errors, 5xx and bad JSON keep the previous verdict (the old 6h
  check revoked all of an account's sessions on any failure, including
  outages).
- GET /uds-auth/session-status (non-sliding) returns alive + tokenValid.
  The client probes it every minute and on focus: a gone session signs the
  UI out with a notice; a rejected token opens a refresh QR once.
- Scanning in refresh mode writes the new token into every live session of
  the account and the skill credential cache in place: no new session, no
  reload. Other accounts are rejected (token_refresh_emp_mismatch).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

uds-auth/docs/skill-auth-standard.zh.md

@@ -119,7 +119,7 @@ def load_uds_skill_auth():
 - 全局共享 token / 把 token 注入 `shellEnv`  
 - SKILL 教打印环境变量中的密钥  
 - 无白名单的开放代理  
-- 用 UI `sessionStore` 的 30min TTL 冒充 skill 长凭证  
+- 用 UI `sessionStore` 的闲置 TTL（`sessionIdleTimeoutHours`）冒充 skill 长凭证  
 - 业务 skill 硬编码插件源码路径（应用 `uds-skill-auth` skill）  
 
 ## 验收