Add five API-key access-review connectors

Add Mercury, Apollo.io, Deepgram, ClickHouse Cloud, and Langfuse as
access-review connectors. All are API-key, single-tenant providers
(Pattern 3): the key identifies one tenant, so there is no OAuth flow,
picker UI, or bootstrap/helm configuration.

- Mercury: Bearer token, GET /api/v1/users, cursor pagination.
- Apollo.io: x-api-key header, GET /api/v1/users/search (teammates).
- Deepgram: Token scheme; lists members across every project and
  dedupes by member_id, unioning per-project scopes.
- ClickHouse Cloud: HTTP Basic (keyId:keySecret); discovers the org
  via GET /v1/organizations, then lists its members.
- Langfuse: HTTP Basic (publicKey:secretKey); a base-URL setting
  selects the regional cloud host or a self-hosted instance.

Each adds the enum value, migration, GraphQL binding, provider
Registration, a driver with a cassette-driven test, and a brand logo.

Signed-off-by: Aurélien Sibiril <81782+aureliensibiril@users.noreply.github.com>

pkg/connector/provider/probe_test.go

@@ -78,6 +78,19 @@ func TestBuildOktaProbeURL(t *testing.T) {
 	assert.Equal(t, "https://acme.okta.com/api/v1/users?limit=1", probeURL)
 }
 
+func TestBuildLangfuseProbeURL(t *testing.T) {
+	t.Parallel()
+
+	conn := &coredata.Connector{Provider: coredata.ConnectorProviderLangfuse}
+	require.NoError(t, conn.SetSettings(&coredata.LangfuseConnectorSettings{
+		BaseURL: "https://us.cloud.langfuse.com",
+	}))
+
+	probeURL, err := buildLangfuseProbeURL(conn)
+	require.NoError(t, err)
+	assert.Equal(t, "https://us.cloud.langfuse.com/api/public/organizations/memberships", probeURL)
+}
+
 func TestBuildPostHogProbeURL(t *testing.T) {
 	t.Parallel()