feat(fusion_clock): auto-wipe clock-in/out photos after a retention window

Privacy/space housekeeping for the kiosk verification selfies. A new daily cron
(_cron_fusion_wipe_old_photos) deletes the photo attachments on attendances
whose clock-in is older than fusion_clock.photo_retention_days (default 60).
Only the images are removed — attendance records, worked hours and penalties
are kept. Clearing the attachment-backed binary reclaims filestore space.

- Configurable in Settings → Fusion Clock → NFC Kiosk ("Auto-Wipe Photos After
  (days)"); set 0 to disable.
- Wipes all three photo fields (NFC check-in/out + legacy portal photo),
  batched with per-batch savepoints.
- tests/test_photo_retention.py covers wipe-old / keep-recent / retention=0.

Verified live on entech (19.0.3.11.7) via a rollback-only dry run: a 70-day
shift's photos were wiped (record + 8h hours preserved) while a 5-day shift's
photo was kept; nothing persisted. 0 attendances currently exceed 60 days.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

fusion_clock/models/res_config_settings.py

@@ -268,6 +268,15 @@ class ResConfigSettings(models.TransientModel):
         help="Which clock location is bound to the NFC kiosk for this company. "
              "Required when the kiosk is enabled.",
     )
+    fclk_photo_retention_days = fields.Integer(
+        string='Auto-Wipe Photos After (days)',
+        config_parameter='fusion_clock.photo_retention_days',
+        default=60,
+        help="Clock-in/out verification photos older than this many days are deleted "
+             "automatically by a daily cron. The attendance record, worked hours and "
+             "penalties are kept — only the images are removed, reclaiming storage. "
+             "Set to 0 to disable the auto-wipe.",
+    )
 
     def set_values(self):
         super().set_values()