Add Google Calendar and Gmail integration via Python SDK

Replaces the gws CLI subprocess approach with google-api-python-client.
Adds get_calendar_events, create_calendar_event, gmail_search_emails, and
gmail_get_email as LangChain tools; all admin-gated and auto-enabled when
token.json is present. Includes uv-runnable scripts/google_auth.py for
one-time OAuth2 setup.

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

.gitignore

@@ -12,6 +12,7 @@ wheels/
 # Environment files
 .env
 credentials.json
+token.json
 
 # Database files
 database/