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>

internal/ocr/worker.go

@@ -6,6 +6,7 @@ import (
 	"log/slog"
 	"strings"
 	"sync"
+	"sync/atomic"
 	"time"
 
 	"archivmail/internal/index"
@@ -38,7 +39,11 @@ type Worker struct {
 	// hour falls inside it, workers stop consuming the queue (jobs stay buffered
 	// in the channel / as ocr_status='pending' in the DB) until it reopens.
 	// nil = never pause (legacy behaviour).
-	pausedHours *[2]int
+	//
+	// Stored as atomic.Pointer so SetPausedHours can be called concurrently
+	// from a signal handler (SIGHUP reload) while run() goroutines read it,
+	// without requiring a process restart to change the window (PROJ-56b).
+	pausedHours atomic.Pointer[[2]int]
 }
 
 // pauseCheckInterval is how often a paused worker re-checks whether the pause
@@ -73,26 +78,35 @@ func NewWorker(store *storage.Store, idxMgr index.TenantIndexer, opts Options) *
 	if opts.Logger == nil {
 		opts.Logger = slog.Default()
 	}
-	return &Worker{
-		store:       store,
-		idxMgr:      idxMgr,
-		logger:      opts.Logger,
-		queue:       make(chan Job, opts.QueueSize),
-		done:        make(chan struct{}),
-		workers:     opts.Workers,
-		langs:       opts.Langs,
-		pausedHours: opts.PausedHours,
+	w := &Worker{
+		store:   store,
+		idxMgr:  idxMgr,
+		logger:  opts.Logger,
+		queue:   make(chan Job, opts.QueueSize),
+		done:    make(chan struct{}),
+		workers: opts.Workers,
+		langs:   opts.Langs,
 	}
+	w.pausedHours.Store(opts.PausedHours)
+	return w
+}
+
+// SetPausedHours updates the pause window at runtime, without requiring a
+// worker/process restart. Pass nil to disable pausing. Safe to call
+// concurrently with running workers (e.g. from a SIGHUP reload handler).
+func (w *Worker) SetPausedHours(hours *[2]int) {
+	w.pausedHours.Store(hours)
 }
 
 // isPaused reports whether the OCR worker should currently hold off processing
 // because the local time falls inside the configured pause window.
 // Supports wrap-around windows where start > end (e.g. [22, 6]).
 func (w *Worker) isPaused(now time.Time) bool {
-	if w.pausedHours == nil {
+	hours := w.pausedHours.Load()
+	if hours == nil {
 		return false
 	}
-	start, end := w.pausedHours[0], w.pausedHours[1]
+	start, end := hours[0], hours[1]
 	if start == end {
 		// Degenerate / no-op window — never pause.
 		return false