fix: Windows build + gosec lint errors (#585)

Fixes Windows build by adding platform-specific inode handling via build tags. Also fixes gosec lint warnings in migrate_tombstones.go.

Thanks @deblasis!

internal/storage/sqlite/freshness_unix.go

@@ -0,0 +1,19 @@
+//go:build !windows
+
+// Package sqlite implements the storage interface using SQLite.
+package sqlite
+
+import (
+	"os"
+	"syscall"
+)
+
+// getFileInode extracts the inode from file info on Unix systems.
+func getFileInode(info os.FileInfo) uint64 {
+	if sys := info.Sys(); sys != nil {
+		if stat, ok := sys.(*syscall.Stat_t); ok {
+			return stat.Ino
+		}
+	}
+	return 0
+}