feat: add Gmail and Calendar context providers

[Mustafa-Esoofally]

Summary

• Add GmailContextProvider and GoogleCalendarContextProvider to Scout's context registry
• Support both service account and OAuth authentication
• Include comprehensive test suites for CRUD operations

Changes

scout/contexts.py

• Import Gmail and Calendar providers from agno 2.6.7
• Add _create_gmail_provider() factory (requires GOOGLE_DELEGATED_USER for SA mode)
• Add _create_calendar_provider() factory (works with SA or OAuth)
• Both providers enable write=True by default

Test Files

• test_google_context_providers.py — basic status and query tests
• test_google_comprehensive.py — full CRUD tests (16 passed, 1 skipped)

Test Results

Operation	Calendar	Gmail
Status	✓	✓
List/Read	✓	✓
Search	✓	✓
Create	✓	✓
Update	✓	✓
Delete	✓	✓
Async	✓	-

Notes

• Gmail OAuth requires ALL scopes (readonly + modify + compose) in one token to avoid read/write toolkit conflicts
• Calendar delete asks for confirmation before deleting (correct safety behavior)
• Requires agno >= 2.6.7 for Gmail and Calendar context providers

Test Plan

• Calendar status check
• Calendar CRUD operations
• Gmail status check
• Gmail CRUD operations
• Test on AgentOS