Update stale API endpoints and model chains

- Instagram: migrate /v1/ to /v2/ ScrapeCreators endpoint (v1 deprecated Feb 2026)
- OpenAI: switch fallback chain to [gpt-5-mini, gpt-4.1-mini, gpt-4.1] (8x cheaper,
  gpt-5-mini is the first mini model supporting web_search with filters.allowed_domains)
- xAI: use explicit grok-4-1-fast-non-reasoning (bare name aliases to reasoning variant)
- xAI: pass from_date/to_date natively to x_search tool config instead of prompt-only
- Polymarket: correct rate limit comment (15K/10s, not 350/10s)

scripts/lib/instagram.py

@@ -217,7 +217,7 @@ def search_instagram(
 
     try:
         resp = _requests.get(
-            f"{SCRAPECREATORS_BASE}/v1/instagram/reels/search",
+            f"{SCRAPECREATORS_BASE}/v2/instagram/reels/search",
             params={"query": core_topic},
             headers=_sc_headers(token),
             timeout=30,
@@ -228,7 +228,7 @@ def search_instagram(
         _log(f"ScrapeCreators error: {e}")
         return {"items": [], "error": f"{type(e).__name__}: {e}"}
 
-    # Items are in the 'reels' array (ScrapeCreators v1 response)
+    # Items are in the 'reels' array (ScrapeCreators v2 response)
     raw_items = data.get("reels") or data.get("items") or data.get("data") or []
 
     # Limit to configured count