Gitea SSRF through Git HTTP redirects in mirrors and fetches

Gitea validated the initial remote URL for push mirrors, wiki remote checks, and fetches of migrated pull request heads, but the subsequent raw Git operations followed HTTP redirects without revalidating the destination. A repository administrator using a policy-allowed endpoint that redirects could make Gitea's Git client send requests to an address that the outbound host policy would otherwise block. The impact depends on the configured policy and the internal services reachable from the server.