Fix progress regex and SIGHUP/scan_zims race condition

- Parse Browsertrix "crawled":N JSON format instead of "N pages"
- Add 3s delay between SIGHUP to kiwix-serve and scan_zims() call
  so the OPDS catalog is reloaded before we query it for linking

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

lib/scraper_runner.py

@@ -339,6 +339,9 @@ def _process_job(job, config, stop_event):
     except Exception as e:
         logger.warning(f"Job {job_id}: failed to signal kiwix-serve: {e}")
 
+    # Wait for kiwix-serve to reload its catalog after SIGHUP
+    time.sleep(3)
+
     zim_source_id = None
     try:
         from .zim_monitor import scan_zims