feat: rebuild web UI on the shared theta42 app stack; OIDC + local admin auth

The web management UI was a bespoke minimal theme with LDAP-bind login.
Rebuild it to match the SSO Manager and Proxy — same stack, same look/feel,
same auth model. The SSH bridge, audit, metrics, and access logic are
unchanged; this is purely the web layer.

Frontend (mirrors proxy/sso):
- Express + EJS with the shared top.ejs/bottom.ejs shell, Bootstrap 5,
  jQuery, jq-repeat, FontAwesome, Socket.IO, and the shared app-base.js /
  val.js client framework (copied verbatim). Vendor libs served from
  node_modules via /static-modules; app assets via /static.
- Dashboard / Sessions / Audit pages render in the common look/feel,
  loading data through the authenticated /api/* endpoints.

Auth (mirrors proxy):
- OIDC against the SSO (utils/oidc.js + routes/auth.js + models/oidc_state)
  plus a local anti-lockout admin (models/user_redis.js, bootstrapped from
  auth.adminUsers[0] / auth.localAdminPass). AuthToken sessions carry the
  group snapshot; middleware gates the data API on adminGroups or the local
  admin. New config: oidc{} + auth.adminUsers/localAdminPass.
- /api/user/me drives the client login state; "Log in with SSO" hidden when
  oidc.enabled is false.

Verified end to end: local admin login -> token -> /api/user/me isAdmin,
metrics/sessions/audit 200 with token / 401 without / 401 bad password;
static + page shells serve; 26 tests green.

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

docs/installation.md

@@ -94,7 +94,8 @@ Every key is documented in
 [`secrets.js.example`](https://github.com/theta42/jump-host/blob/master/secrets.js.example):
 `ldap` (bind + bases + TLS), `sso` (url + apiToken), `ssh`
 (`listenPort`, `passwordAuth`, `allowRawIPs`, `keyComment`, timeouts,
-`maxSessions`), `web.port`, `auth.adminGroups`, and `redis`.
+`maxSessions`), `web.port`, `oidc` (web-UI SSO login), `auth`
+(`adminGroups` / `adminUsers` / `localAdminPass`), and `redis`.
 
 ## Verifying