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/coredata/connector_settings.go

@@ -156,6 +156,15 @@ type (
 	NeonConnectorSettings struct {
 		OrganizationID string `json:"organization_id"`
 	}
+
+	// LangfuseConnectorSettings carries the Langfuse API base URL, which
+	// spans the regional cloud hosts (cloud.langfuse.com /
+	// us.cloud.langfuse.com / …) and self-hosted instances. The
+	// organization-scoped API key is bound to a single organization on
+	// that host, so the base URL is the only per-tenant setting.
+	LangfuseConnectorSettings struct {
+		BaseURL string `json:"base_url"`
+	}
 )
 
 // GrantType returns the OAuth2 grant type recorded on the connector's