When storage.direct_serve is enabled and the backend supports it (S3,
Azure), cached artifact downloads return a 302 redirect to a presigned
URL instead of streaming bytes through the proxy. Falls back to
streaming when the backend can't sign (fileblob, local filesystem) or
signing fails.
Adds the azureblob driver so azblob:// storage URLs work.
Cache-hit accounting already happened before io.Copy so redirects are
counted correctly; the metrics calls are pulled into a helper so both
paths share them.
Closes#96
* Fix all golangci-lint issues across the codebase
Resolve 77 lint issues reported by golangci-lint with gocritic, gocognit,
gocyclo, maintidx, dupl, mnd, unparam, ireturn, goconst, and errcheck
enabled. Net reduction of ~175 lines through shared helpers and
deduplication.
* Suppress staticcheck SA1019 for intentional deprecated field usage
The Storage.Path field is deprecated but still read for backwards
compatibility with existing configs that haven't migrated to the URL field.
