fix: audit findings — edge cases in paginate, output, run

- paginate.py: max(nums) on empty set → guard
- paginate.py: HEAD fallback to GET if server doesn't support HEAD
- output.py: disk health check every 500 topics
- run.py: avoid page-1 extra redirect
- __main__.py: URL validation (must contain vwts.ru)

vwts_scraper/run.py

@@ -48,7 +48,8 @@ def run(section_url: str):
             consecutive_404 = 0
             continue
 
-        url = f"{section_url}page-{pg}"
+        # page-1 = базовый URL (чтобы не было лишнего редиректа)
+        url = section_url if pg == 1 else f"{section_url}page-{pg}"
         log.info(f"📄 [{pg}/{total_pages}]")
 
         page_soup = get(url)