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.go

@@ -314,6 +314,25 @@ func buildMetabaseProbeURL(conn *coredata.Connector) (string, error) {
 	return endpoint.String(), nil
 }
 
+func buildLangfuseProbeURL(conn *coredata.Connector) (string, error) {
+	s, err := coredata.ConnectorSettings[coredata.LangfuseConnectorSettings](conn)
+	if err != nil {
+		return "", fmt.Errorf("cannot read langfuse connector settings: %w", err)
+	}
+
+	baseURL, err := normalizeLangfuseBaseURL(s.BaseURL)
+	if err != nil {
+		return "", err
+	}
+
+	u, err := url.Parse(baseURL)
+	if err != nil {
+		return "", fmt.Errorf("cannot parse langfuse base URL: %w", err)
+	}
+
+	return u.JoinPath("api", "public", "organizations", "memberships").String(), nil
+}
+
 func buildSigNozProbeURL(conn *coredata.Connector) (string, error) {
 	s, err := coredata.ConnectorSettings[coredata.SigNozConnectorSettings](conn)
 	if err != nil {