httpx ignores the client-level `limits` kwarg when a custom `transport`
is supplied. The #31599 keepalive fix injected limits via
`httpx_kwargs[limits]`, but the fallback-IP branch also passes a
custom `TelegramFallbackTransport` — so the limits were silently
discarded and the inner AsyncHTTPTransport instances ran with httpx
defaults (keepalive_expiry=5.0), leaking CLOSE_WAIT fds.
Pass the tuned limits directly into `TelegramFallbackTransport`
via `transport_kwargs` so its inner transports honour keepalive_expiry.
Only affects the fallback-IP branch; proxy and direct-DNS branches
continue to use `_with_limits()` as before.
Fixes#58790
01ee312de6