feat: v2.8 — Instagram Reels source + TikTok ScrapeCreators migration

Add Instagram Reels as the 8th research source via ScrapeCreators API.
One API key (SCRAPECREATORS_API_KEY) now covers both TikTok and Instagram.

- Add scripts/lib/instagram.py: keyword search, transcript extraction,
  relevance scoring, engagement metrics (views, likes, comments)
- Add InstagramItem to schema, normalization, scoring, dedup, rendering
- Add Instagram to orchestrator pipeline, watchlist, and UI spinners
- Update SKILL.md: stats template, citation priority, item format,
  URL-to-name extraction rules, anti-Sources instruction
- Update README and CHANGELOG for v2.8
- Fix: Instagram/TikTok not running in --search= web-only path
- Fix: web stats line showing full URLs instead of domain names
- Replace APIFY_API_TOKEN with SCRAPECREATORS_API_KEY throughout

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

scripts/lib/env.py

@@ -421,6 +421,20 @@ def get_tiktok_token(config: Dict[str, Any]) -> str:
     return config.get('SCRAPECREATORS_API_KEY') or config.get('APIFY_API_TOKEN') or ''
 
 
+def is_instagram_available(config: Dict[str, Any]) -> bool:
+    """Check if Instagram source is available (ScrapeCreators).
+
+    Returns True if SCRAPECREATORS_API_KEY is set.
+    Instagram uses the same key as TikTok.
+    """
+    return bool(config.get('SCRAPECREATORS_API_KEY'))
+
+
+def get_instagram_token(config: Dict[str, Any]) -> str:
+    """Get Instagram API token (same ScrapeCreators key as TikTok)."""
+    return config.get('SCRAPECREATORS_API_KEY') or ''
+
+
 # Backward compat alias
 is_apify_available = is_tiktok_available