Update README for V2 and bump USER_AGENT to 2.0

- Add V2 to title
- Document Bird CLI installation (free X search)
- Add --days=N to options table
- Update Requirements to show Bird CLI as recommended free option
- Replace How It Works with two-phase search architecture
- Add What's New in V2 section with all new features
- Credit community contributors (@JosephOIbrahim, @levineam, @jonthebeef)
- Bump http.py USER_AGENT from 1.0 to 2.0

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

scripts/lib/http.py

@@ -20,7 +20,7 @@ def log(msg: str):
         sys.stderr.flush()
 MAX_RETRIES = 3
 RETRY_DELAY = 1.0
-USER_AGENT = "last30days-skill/1.0 (Claude Code Skill)"
+USER_AGENT = "last30days-skill/2.0 (Claude Code Skill)"
 
 
 class HTTPError(Exception):