Hide connectors that need admin setup; they start turned off

A connector's enabled switch is now optional: unset means on when the
connector has the server settings it needs, so Google Drive, SharePoint
and Confluence start off until their OAuth settings are present, and an
admin's explicit switch always wins. Changing only the sharing mode no
longer switches a connector on.

Members only see connectors they can use. The catalog, Add Source tiles
and Add Tool leave out anything turned off or still needing setup, except
a connector a member already has a connection to, which stays listed as
turned off so it can be managed or removed.

docs/content/Guides/Integrations/google-drive-connector.mdx

@@ -68,7 +68,7 @@ Restart your application, then go to **Settings > Connectors** and pick **Google
 
 ## Troubleshooting
 
-- **Shows Needs admin setup** — `GOOGLE_CLIENT_ID` or `GOOGLE_CLIENT_SECRET` is missing from the backend `.env`. Admin > Connectors lists which one.
+- **Google Drive is not offered** — `GOOGLE_CLIENT_ID` or `GOOGLE_CLIENT_SECRET` is missing from the backend `.env`, so the connector stays off. Admin > Connectors lists which one.
 - **Authentication failed** — Check that the redirect URI matches exactly and equals `CONNECTOR_REDIRECT_BASE_URI`, with no query parameters. Ensure the Google Drive API is enabled.
 - **Sign-in popup closes but the account never connects** — The frontend origin is not allowed to receive the result. Add it to `CONNECTOR_ALLOWED_ORIGINS` in the backend `.env`.
 - **Permission denied** — Verify the OAuth consent screen is configured and the user has access to the target files.