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/utils/roles.js

@@ -0,0 +1,110 @@
+'use strict';
+
+/**
+ * Pure authorization role logic — no redis, no I/O — so it can be unit tested
+ * in isolation. models/grant.js supplies the data (grant records, owned
+ * domains, conf.auth) and this module collapses it into effective rights and
+ * answers allow/deny questions.
+ *
+ * Roles rank: admin > manager (owner/full over a domain) > viewer.
+ */
+
+const ROLE_RANK = {viewer: 1, manager: 2, admin: 3};
+
+function rank(role){
+	return ROLE_RANK[role] || 0;
+}
+
+// Whichever of two roles is stronger; either may be null/undefined.
+function maxRole(a, b){
+	if(rank(a) >= rank(b)) return a || b || null;
+	return b || a || null;
+}
+
+/**
+ * Collapse config, grants, and ownership into effective rights.
+ *
+ * @param {Object} identity - {username, groups: string[]}
+ * @param {Object} data
+ *   - grants: [{subjectType, subject, scope, domain, role}]
+ *   - ownedDomains: string[] (domains the user owns via created_by)
+ *   - authConf: conf.auth ({adminUsers, adminGroups, groupRoleMap})
+ * @returns {Object} { isAdmin, global: role|null, domains: {domain: role} }
+ */
+function resolveEffective(identity, data){
+	let username = identity && identity.username;
+	let groups = (identity && identity.groups) || [];
+	let grants = (data && data.grants) || [];
+	let ownedDomains = (data && data.ownedDomains) || [];
+	let authConf = (data && data.authConf) || {};
+
+	let result = {isAdmin: false, global: null, domains: {}};
+
+	// 1) Config-driven global admin (anti-lockout bootstrap).
+	if((authConf.adminUsers || []).includes(username)) result.isAdmin = true;
+	for(let g of groups){
+		if((authConf.adminGroups || []).includes(g)) result.isAdmin = true;
+	}
+
+	// 2) Config-driven group role defaults.
+	let groupRoleMap = authConf.groupRoleMap || {};
+	for(let g of groups){
+		let m = groupRoleMap[g];
+		if(!m) continue;
+		if(m.role === 'admin' && (m.scope === 'global' || !m.scope)){
+			result.isAdmin = true;
+		}else if(m.scope === 'global'){
+			result.global = maxRole(result.global, m.role);
+		}else if(m.domain){
+			result.domains[m.domain] = maxRole(result.domains[m.domain], m.role);
+		}
+	}
+
+	// 3) Grant records for this user or any of their groups.
+	for(let grant of grants){
+		let matches = (grant.subjectType === 'user' && grant.subject === username)
+			|| (grant.subjectType === 'group' && groups.includes(grant.subject));
+		if(!matches) continue;
+
+		if(grant.scope === 'global'){
+			if(grant.role === 'admin') result.isAdmin = true;
+			else result.global = maxRole(result.global, grant.role);
+		}else{
+			result.domains[grant.domain] = maxRole(result.domains[grant.domain], grant.role);
+		}
+	}
+
+	// 4) Ownership: manager rights over every owned domain.
+	for(let domain of ownedDomains){
+		result.domains[domain] = maxRole(result.domains[domain], 'manager');
+	}
+
+	return result;
+}
+
+// Effective role on one domain, folding in admin and any global role.
+function roleForDomain(effective, domain){
+	if(effective.isAdmin) return 'admin';
+	return maxRole(effective.global, effective.domains[domain]);
+}
+
+// Does `effective` meet or exceed `minRole` for `domain`?
+function allows(effective, minRole, domain){
+	return rank(roleForDomain(effective, domain)) >= rank(minRole);
+}
+
+// Domain names the identity can at least view (excludes the global-role case,
+// which callers treat as "sees everything").
+function visibleDomains(effective){
+	return Object.keys(effective.domains).filter(d => rank(effective.domains[d]) >= rank('viewer'));
+}
+
+module.exports = {
+	ROLE_RANK,
+	rank,
+	maxRole,
+	resolveEffective,
+	roleForDomain,
+	allows,
+	visibleDomains,
+};