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).

alerting/internal/config/config.go

@@ -13,6 +13,7 @@ type Config struct {
 	HTTPListenAddr    string
 	Postgres          PostgresConfig
 	APIQueryURL       string // base URL of /api, e.g. http://api:8080 -- alerting never talks to ClickHouse/Tantivy directly
+	APIServiceToken   string // RoleService credential presented to /api's POST /query -- see queryclient.New's doc comment
 	CORSAllowedOrigin string
 	Evaluator         EvaluatorConfig
 }
@@ -52,6 +53,10 @@ func Load() (Config, error) {
 			Password: getenv("POSTGRES_PASSWORD", ""),
 		},
 		APIQueryURL: getenv("API_QUERY_URL", "http://localhost:8080"),
+		// Empty by default -- matches Phase 0-3 behavior for a
+		// single-tenant deployment with no enterprise/ deployed (api's
+		// authorizer is nil there, so an absent token is fine).
+		APIServiceToken: getenv("API_SERVICE_TOKEN", ""),
 		// Same "no auth yet" tradeoff as api's CORSAllowedOrigin default --
 		// see api/internal/config/config.go's comment, same reasoning here.
 		CORSAllowedOrigin: getenv("CORS_ALLOWED_ORIGIN", "*"),