fix: review findings for lazysecrets list: recent means the last 90 days, cache saves lock and keep deletions and the TUI's cursors, failed lists aren't retried, one expiry rule

internal/cachefile/lock_unix.go

@@ -0,0 +1,25 @@
+//go:build unix
+
+package cachefile
+
+import (
+	"os"
+	"syscall"
+)
+
+// lock takes path as a lock file, waiting while another lazysecrets has
+// it, and returns how to let go.
+func lock(path string) (unlock func(), err error) {
+	f, err := os.OpenFile(path, os.O_CREATE|os.O_RDWR, 0o600)
+	if err != nil {
+		return nil, err
+	}
+	if err := syscall.Flock(int(f.Fd()), syscall.LOCK_EX); err != nil {
+		f.Close()
+		return nil, err
+	}
+	return func() {
+		_ = syscall.Flock(int(f.Fd()), syscall.LOCK_UN)
+		f.Close()
+	}, nil
+}