feat(PROJ-56): OCR-Pausenfenster per SIGHUP-Reload statt Restart

paused_hours konnte bisher nur über einen vollen Prozess-Restart geändert
werden, was SMTP/IMAP/API unnötig unterbricht. Worker.pausedHours ist jetzt
ein atomic.Pointer mit SetPausedHours(); SIGHUP liest config.yml neu und
aktualisiert nur die OCR-Pausenzeit im laufenden Prozess. Neue
deploy/cron.d/archivmail-ocr-pause(.sh) lässt Admins die Pausenzeiten direkt
in der Cron-Datei pflegen und löst per systemctl reload statt restart aus.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

cmd/archivmail/main.go

@@ -474,6 +474,17 @@ func main() {
 		}
 	}()
 
+	// PROJ-56b: SIGHUP reloads only the OCR pause window from config.yml, so
+	// admins/cron can change paused_hours without a full service restart
+	// (which would otherwise drop SMTP/IMAP connections unnecessarily).
+	reload := make(chan os.Signal, 1)
+	signal.Notify(reload, syscall.SIGHUP)
+	go func() {
+		for range reload {
+			reloadOCRPauseWindow(*configPath, ocrWorker, logger)
+		}
+	}()
+
 	// Graceful shutdown
 	quit := make(chan os.Signal, 1)
 	signal.Notify(quit, syscall.SIGINT, syscall.SIGTERM)
@@ -485,6 +496,25 @@ func main() {
 	httpServer.Shutdown(ctx)
 }
 
+// reloadOCRPauseWindow re-reads config.yml and applies any change to
+// ocr.paused_hours to the already-running OCR worker, without restarting
+// the process. Other config sections are intentionally ignored — a full
+// reload of e.g. DB DSN or listen ports would require a restart anyway.
+func reloadOCRPauseWindow(configPath string, ocrWorker *ocr.Worker, logger *slog.Logger) {
+	cfg, err := config.Load(configPath)
+	if err != nil {
+		logger.Warn("sighup reload: config read failed, keeping current pause window", "err", err)
+		return
+	}
+	ocrWorker.SetPausedHours(cfg.OCR.PausedHours)
+	if cfg.OCR.PausedHours != nil {
+		logger.Info("sighup reload: ocr pause window updated",
+			"from_hour", cfg.OCR.PausedHours[0], "to_hour", cfg.OCR.PausedHours[1])
+	} else {
+		logger.Info("sighup reload: ocr pause window cleared")
+	}
+}
+
 // submitToWorker parses a raw email and submits it to the async index worker.
 // tenantID may be nil for global context.
 // If ocrWorker is non-nil and the mail has attachments, an OCR job is also