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).

api/internal/authz/authz_test.go

@@ -0,0 +1,36 @@
+package authz
+
+import "testing"
+
+func TestRoleSatisfies(t *testing.T) {
+	tests := []struct {
+		have, want Role
+		satisfies  bool
+	}{
+		{RoleViewer, RoleViewer, true},
+		{RoleEditor, RoleViewer, true},
+		{RoleAdmin, RoleViewer, true},
+		{RoleOwner, RoleViewer, true},
+		{RoleViewer, RoleEditor, false},
+		{RoleViewer, RoleAdmin, false},
+		{RoleEditor, RoleAdmin, false},
+		{RoleAdmin, RoleOwner, false},
+		{RoleOwner, RoleOwner, true},
+		// RoleService is a separate lane, not on the human rank scale --
+		// per /docs/phase-4-isolation-design.md's alerting service
+		// identity, it must never satisfy a human role requirement no
+		// matter how "high" that might look on paper, and a human role
+		// (even Owner) must never satisfy a RoleService requirement.
+		{RoleService, RoleViewer, false},
+		{RoleService, RoleOwner, false},
+		{RoleOwner, RoleService, false},
+		{RoleViewer, RoleService, false},
+		{RoleService, RoleService, true},
+	}
+	for _, tt := range tests {
+		got := tt.have.Satisfies(tt.want)
+		if got != tt.satisfies {
+			t.Errorf("Role(%q).Satisfies(%q) = %v, want %v", tt.have, tt.want, got, tt.satisfies)
+		}
+	}
+}