Add OIDC login and per-domain authorization

Authentication previously implied full authorization: any valid token
could manage every host, DNS provider, domain, and user. This adds SSO
login and a per-domain rights model.

OIDC login (authorization_code + PKCE):
- conf.oidc + conf.auth blocks; clientSecret in (gitignored) secrets.js.
- utils/oidc.js (state/PKCE, code exchange, userinfo) using global fetch.
- models/oidc_state.js: short-lived state store, auto-expiring via
  model-redis 1.5 per-key TTL.
- routes/auth.js: GET /auth/oidc/start + /auth/oidc/callback; JIT-provisions
  a local user, mints an AuthToken carrying the SSO groups, hands the token to
  the browser via a URL fragment. "Log in with SSO" button on the login page.

Authorization (groups + app overrides, per-domain, with ownership):
- models/grant.js + utils/roles.js (pure, unit-tested): effective rights from
  conf.auth (admin users/groups, group->role map), Grant records
  (user|group -> global|domain -> viewer|manager|admin), and ownership
  (created_by). Roles rank admin > manager(owner) > viewer.
- AuthToken stores session groups; middleware/auth.js exposes req.groups.
- middleware/authz.js: requireAdmin, requireDomainRole(minRole, resolveDomain),
  filterViewable. Applied across routes: host mutations need manager on the
  host's domain; reads are filtered to visible domains; DNS providers, user
  management, and grant management are global-admin-only; certs need viewer.
- routes/grant.js: admin CRUD for grants. Anti-lockout via conf.auth.adminUsers
  plus migrations/grant_bootstrap.js.

Frontend: /me returns effective rights; nav gates Users/Grants to admins;
grants management page; OIDC token-fragment handling in app-base.js.

Tests: utils/roles and utils/oidc unit-tested (no redis); wired into the test
scripts. Full suite 89 pass. Also verified end-to-end against redis (grant
resolution, middleware allow/deny/403, list filtering) and the OIDC pure flow.

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

nodejs/models/user_redis.js

@@ -2,6 +2,7 @@
 
 const Table = require('.');
 const bcrypt = require('bcrypt');
+const crypto = require('crypto');
 const saltRounds = 10;
 
 class User extends Table{
@@ -40,6 +41,28 @@ class User extends Table{
 		}
 	}
 
+	/**
+	 * Just-in-time provisioning for an OIDC-authenticated user. Creates the
+	 * local user on first login so relations (tokens, created_by, grants) have
+	 * something to point at. OIDC users get a random, unusable password — they
+	 * authenticate through the SSO, never the local password form.
+	 *
+	 * @param {Object} data - {username, ...} from the OIDC userinfo claims
+	 * @returns {User} the existing or newly created user
+	 */
+	static async upsertOidc(data){
+		try{
+			return await User.get(data.username);
+		}catch(error){
+			return await User.create({
+				username: data.username,
+				password: crypto.randomBytes(24).toString('hex'),
+				created_by: data.username,
+				backing: 'oidc',
+			});
+		}
+	}
+
 	static async login(data){
 		try{
 			let user = await User.get(data);