feat(keycloak): M4.3 — Admin API adapter + claim resolver

internal/keycloak/ — Adapter interface with two implementations:
  HTTPAdapter  cached client-credentials token; CreateOrgAndInvite +
               SyncClaims + Health against the real KC Admin API.
  Mock         in-process map for unit tests + dev convenience when
               KEYCLOAK_ADMIN_URL is empty. Used by the eachStore harness.

POST /v1/tenants now accepts admin_email + admin_name. When set, the
adapter creates a KC organization, invites the user as IT_ADMIN, and
triggers VERIFY_EMAIL + UPDATE_PASSWORD. Response wraps the tenant
with TenantCreated{tenant, invite_url}. KC failures DO NOT roll the
tenant back — they emit a keycloak.provision_failed audit event.
Successful invites emit keycloak.invite_sent.

POST /v1/internal/keycloak/claims resolves a tenant's current claim
bundle (tenant_id, slug, products, plan, status). Lookup chain:
body.tenant_id → body.tenant_slug → user_attrs.tenant_id →
user_attrs.tenant_slug.

Config: KEYCLOAK_ADMIN_URL / REALM / CLIENT_ID / CLIENT_SECRET;
empty URL falls back to Mock.

Tests:
  internal/keycloak/mock_test.go     conflict surfacing, FailNext hook,
                                     SyncClaims persistence.
  internal/keycloak/client_test.go   HTTPAdapter against an in-process
                                     stub KC: health, full create-org-
                                     and-invite, conflict, token-cache,
                                     401 retry, ErrUnavailable.
  internal/server/keycloak_test.go   eachStore integration: provisions
                                     via mock; failure path emits
                                     provision_failed audit; claims
                                     endpoint via every lookup variant
                                     + 404 + 400.

OpenAPI extended with TenantCreated + Claims schemas and the new
claims endpoint. Contract test asserts the new path.

CI: include internal/keycloak/... in the test package list so
HTTPAdapter coverage counts. Total project line coverage: 71.6%.

Refs: M4.3

internal/server/tenants_test.go

@@ -24,9 +24,12 @@ func TestCreateTenant(t *testing.T) {
 		if resp.StatusCode != http.StatusCreated {
 			t.Fatalf("status = %d, body=%s", resp.StatusCode, body)
 		}
-		t1 := decode[store.Tenant](t, body)
-		if t1.Slug != "beta-co" || t1.Status != "trial" || t1.Plan != "starter" {
-			t.Errorf("unexpected: %+v", t1)
+		out := decode[struct {
+			Tenant    *store.Tenant `json:"tenant"`
+			InviteURL string        `json:"invite_url"`
+		}](t, body)
+		if out.Tenant.Slug != "beta-co" || out.Tenant.Status != "trial" || out.Tenant.Plan != "starter" {
+			t.Errorf("unexpected: %+v", out.Tenant)
 		}
 	})
 }
@@ -81,7 +84,10 @@ func TestActivateTenant(t *testing.T) {
 		_, body := h.do("POST", "/v1/tenants", map[string]any{
 			"slug": "trial-co", "name": "Trial Co.",
 		})
-		created := decode[store.Tenant](t, body)
+		createdWrap := decode[struct {
+			Tenant *store.Tenant `json:"tenant"`
+		}](t, body)
+		created := createdWrap.Tenant
 		if created.Status != "trial" {
 			t.Fatalf("precondition: %q", created.Status)
 		}