Find providers in the registry by the external services they reach

[Lee-W]

The names people type into registry search are often the service they want to talk to, not the Airflow distribution that talks to it -- "openai" or "ollama" rather than "common-ai". Those names were declared in provider.yaml and rendered in a table on the provider page, but neither search path read them, so the queries most likely to lead someone to Common AI returned nothing.

Both search paths now read the same deduped list off the same field, so a query that works in the global search box also works in the /providers/ filter box.

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