Move the webhook SSRF guard into a shared internal/ssrf package and wire it
into every place the server fetches an admin-set URL: webhooks, OIDC discovery,
the AI provider base URL, and custom AI tool calls. Add a global [ssrf] config
block, off by default with an allowed_cidrs bypass, so single-tenant self-hosters
keep reaching internal hosts while multi-tenant or hosted deploys can turn it on.
The old [webhook] allowed_hosts key is still read for backward compat and folds
into the guard.
Abhinav Raut