Add product pagination and enable BestBuy

Implement client-side pagination for the products grid: add PRODUCTS_PER_PAGE, currentProductPage, offset in /products requests, renderPagination(), and changeProductPage() (with smooth scroll). Reset page when filters or event filters change and render empty-state pagination. Add pagination container to the template and styles for pagination buttons and info. Also enable "bestbuy" in SITES_ENABLED in config.py and add a taskkill line to .claude/settings.local.json for closing stray python.exe processes.

.claude/settings.local.json

@@ -14,7 +14,8 @@
       "Bash(python3 -c \"import json,sys; d=json.load\\(sys.stdin\\); print\\(''''Last sync:'''', d[''''last_sync'''']\\); print\\(''''Products:'''', len\\(d[''''products'''']\\)\\); print\\(''''Sample names:''''\\); [print\\('''' -'''', p[''''name''''][:80]\\) for p in d[''''products''''][:5]]\")",
       "Bash(PYTHON=\"/c/Users/hocke/Documents/GitHub/pokemon-stock-checker/.venv/Scripts/python.exe\")",
       "Bash(\"$PYTHON\" -c \":*)",
-      "Bash(1 grep:*)"
+      "Bash(1 grep:*)",
+      "Bash(taskkill /F /IM python.exe)"
     ]
   }
 }