Add README, LICENSE, Makefile, Dockerfile, and CI

Add a detailed README, WTFPL LICENSE, and build/CI tooling modeled on
the vaultik repo (Makefile, multi-stage digest-pinned Dockerfile,
.gitea/workflows/check.yml). Bump Go to 1.26.4 and pin golangci-lint
to v2.12.2. gofmt existing sources so the new fmt-check gate passes.

internal/bsdaily/copy.go

@@ -69,4 +69,4 @@ func CopyFile(src, dst string) (err error) {
 		"elapsed", elapsed.Round(time.Millisecond),
 		"throughput_mbps", fmt.Sprintf("%.1f", throughputMBps))
 	return nil
-}
+}

internal/bsdaily/copy_linux.go

@@ -3,8 +3,8 @@
 package bsdaily
 
 import (
-	"os"
 	"golang.org/x/sys/unix"
+	"os"
 )
 
 func applyFileAdvice(file *os.File, size int64) {
@@ -13,4 +13,4 @@ func applyFileAdvice(file *os.File, size int64) {
 	_ = unix.Fadvise(fd, 0, size, 2)
 	// POSIX_FADV_WILLNEED = 3 - prefetch file into cache
 	_ = unix.Fadvise(fd, 0, size, 3)
-}
+}

internal/bsdaily/copy_other.go

@@ -6,4 +6,4 @@ import "os"
 
 func applyFileAdvice(file *os.File, size int64) {
 	// Fadvise not available on this platform
-}
+}