Add config('trypost.security.allow_private_network') (env TRYPOST_ALLOW_PRIVATE_NETWORK, default off) so self-hosted operators can reach their own internal network; only the private-IP rejection is bypassed, scheme/host checks always apply. Add SafeHttpFetcher::guardedRequest() and route the last unguarded user-supplied-URL fetches through it: the Unsplash/Giphy asset import, the API/MCP attach-media-from-URL download, and the OAuth avatar download. Our-own-storage reads (media crop, Bluesky media) are intentionally left unguarded so internal storage keeps working when self-hosted.
