Remove dead Go code identified by deadcode analysis (#2979)
* remove dead code: pkg/web, pkg/http, and unused env helpers
These packages were confirmed unreachable by deadcode analysis.
pkg/web (Replicate API client) and pkg/http (auth transport) lost
their callers when the push flow moved to the custom registry pusher.
Also removes the orphaned BuildInfo struct and Push function from
pkg/docker/push.go, and the WebHost/APIHost env helpers that only
those packages used.
* remove dead code: fast-build leftovers, old docker CLI client, config helpers, console/shell utils, predict inputs
* fmt: fix trailing newline in docker/errors.go
