Phase 4: SSO scaffolding, RBAC enforcement, tenant-scoped dashboards, audit logging, K8s deployment

RBAC (api/internal/authz) is live on /query and /dashboards, backed by a
new enterprise/ module (session issuance, audit logging, RBAC storage,
OIDC/SAML protocol wiring) that core never imports -- only calls over
HTTP. Found and fixed a real cross-tenant vulnerability in dashboards
(no tenant_id filtering at all) while writing the threat model doc.

Two things are explicitly NOT done, documented rather than hidden:
tenant isolation for log data itself (/query still shares one ClickHouse
connection and Tantivy index across every tenant -- RBAC controls who
can query, not what a query can see), and human SSO login (protocol
wiring exists, no HTTP handler calls it yet). See
docs/security/threat-model.md and docs/phase-4-runbook.md.

Also adds deploy/ (Go Operator + Helm chart, validated offline only --
no cluster was reachable in this environment).

web/src/routes/settings/+page.svelte

@@ -0,0 +1,66 @@
+<script lang="ts">
+	import { getAuthFeatures, enterpriseAuthBase, type AuthFeatures } from '$lib/api';
+
+	let loading = $state(true);
+	let features = $state<AuthFeatures>({ sso_configured: false, oidc_enabled: false, saml_enabled: false });
+
+	async function load() {
+		loading = true;
+		features = await getAuthFeatures();
+		loading = false;
+	}
+	load();
+</script>
+
+<main>
+	<h1>Settings</h1>
+
+	<section>
+		<h2>Core</h2>
+		<p>Single-tenant deployment settings live here. Nothing configurable yet.</p>
+	</section>
+
+	{#if loading}
+		<p>Loading…</p>
+	{:else if features.sso_configured}
+		<section>
+			<h2>Single sign-on</h2>
+			<ul>
+				{#if features.oidc_enabled}<li>OIDC configured</li>{/if}
+				{#if features.saml_enabled}<li>SAML configured</li>{/if}
+			</ul>
+			<p class="note">
+				User/role management isn't built yet -- an Admin or Owner will manage tenant members here once
+				it is.
+			</p>
+		</section>
+	{:else if enterpriseAuthBase}
+		<section>
+			<h2>Single sign-on</h2>
+			<p class="note">enterprise-auth is deployed but no SSO provider is configured yet.</p>
+		</section>
+	{/if}
+	<!-- No section at all when enterpriseAuthBase is unset -- a Phase 0-3-style
+	     single-tenant deployment with no enterprise/ deployed sees a settings
+	     page with core content only, no dead "upgrade to unlock" link. See
+	     /docs/phase-4-rbac-design.md's "Web UI boundary" section. -->
+</main>
+
+<style>
+	main {
+		font-family: system-ui, sans-serif;
+		max-width: 960px;
+		margin: 2rem auto;
+		padding: 0 1rem;
+	}
+	section {
+		margin-bottom: 1.5rem;
+	}
+	h2 {
+		font-size: 1.1rem;
+	}
+	.note {
+		color: #666;
+		font-size: 0.85rem;
+	}
+</style>