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/__main__.py

@@ -25,8 +25,8 @@ logging.basicConfig(
 )
 
 if __name__ == "__main__":
-    if len(sys.argv) < 2:
-        print("❌ Укажи URL раздела. Пример:")
+    if len(sys.argv) < 2 or "vwts.ru" not in sys.argv[1]:
+        print("❌ Укажи URL раздела vwts.ru. Пример:")
         print("   python -m vwts_scraper "
               "https://vwts.ru/forum/vag/benzinovye-dvigateli/")
         sys.exit(1)