* feat(connector): delegate add_resource imports to external Connector
Opt-in integration that routes add_resource data fetching and parsing
to external Connector service; the Connector stages source data and
calls back into OV through the standard add_resource pipeline.
- add ConnectorClient wrapping the control plane's inner doc/add and
task/info endpoints
- add [connector] config section: enable, connector/tracker endpoint
URLs, timeout_seconds, poll_interval_ms, allowed_add_types
- route add_resource via Connector when enabled and args.add_type is
in allowed_add_types; otherwise fall back to the standard pipeline
with an info log
- track imports as connector_import TaskRecords and poll Connector
task status in the background until terminal state or timeout
* fix(connector): delegate add_resource imports to external Connector
