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/server_test.go

@@ -21,6 +21,7 @@ import (
 	tcpostgres "github.com/testcontainers/testcontainers-go/modules/postgres"
 
 	"gitea.meghsakha.com/platform/tenant-registry/internal/config"
+	"gitea.meghsakha.com/platform/tenant-registry/internal/keycloak"
 	"gitea.meghsakha.com/platform/tenant-registry/internal/server"
 	"gitea.meghsakha.com/platform/tenant-registry/internal/store"
 	"gitea.meghsakha.com/platform/tenant-registry/migrations"
@@ -33,6 +34,7 @@ type testHarness struct {
 	srv    *httptest.Server
 	store  store.Store
 	tenant *store.Tenant // pre-created acme tenant
+	kcMock *keycloak.Mock
 }
 
 func (h *testHarness) Close() {
@@ -131,14 +133,19 @@ func newPostgresHarness(t *testing.T) *testHarness {
 func wireHarness(t *testing.T, s store.Store, seed *store.Tenant) *testHarness {
 	t.Helper()
 	logger := slog.New(slog.NewTextHandler(io.Discard, nil))
+	mock := keycloak.NewMock()
 	handler := server.NewRouter(&server.Server{
-		Cfg: &config.Config{Env: "dev"}, Log: logger, Store: s,
+		Cfg:      &config.Config{Env: "dev"},
+		Log:      logger,
+		Store:    s,
+		Keycloak: mock,
 	})
 	return &testHarness{
 		t:      t,
 		srv:    httptest.NewServer(handler),
 		store:  s,
 		tenant: seed,
+		kcMock: mock,
 	}
 }