fix(logs): resolve time ranges using client local time zone for logs commands

internal/journal/journal.go

@@ -6,6 +6,7 @@ import (
 	"fmt"
 	"io"
 	"os/exec"
+	"time"
 
 	"github.com/psviderski/uncloud/pkg/api"
 )
@@ -31,11 +32,11 @@ func logs(ctx context.Context, unit string, opts api.ServiceLogsOptions) (io.Rea
 
 	if opts.Since != "" {
 		args = append(args, "-S")
-		args = append(args, opts.Since)
+		args = append(args, journalTimestamp(opts.Since))
 	}
 	if opts.Until != "" {
 		args = append(args, "-U")
-		args = append(args, opts.Until)
+		args = append(args, journalTimestamp(opts.Until))
 	}
 
 	cmd := commandContext(ctx, journalctl, args...)
@@ -51,6 +52,18 @@ func logs(ctx context.Context, unit string, opts api.ServiceLogsOptions) (io.Rea
 	return p, cmd.Wait, nil
 }
 
+// journalTimestamp formats normalised client timestamps for journalctl versions that do not
+// accept RFC 3339 timezone suffixes. Support for timestamps containing T and Z was added in
+// systemd 255 (6 December 2023). Debian 12 ships systemd 252, so it still needs this conversion.
+// Journald timestamps have microsecond precision.
+func journalTimestamp(value string) string {
+	if t, err := time.Parse(time.RFC3339Nano, value); err == nil {
+		return t.UTC().Format("2006-01-02 15:04:05.999999") + " UTC"
+	}
+	// Preserve raw filters from older clients and SDK callers.
+	return value
+}
+
 // follow synchronously follows the io.Reader, writing each new journal entry to channel.
 // It stops when the reader is exhausted or the context is cancelled.
 func follow(ctx context.Context, reader io.Reader, outCh chan api.LogEntry) {