Fix Cursor CLI for background execution - use stream-json

Fix scheduler interval precision: Use seconds instead of minutes

fix: Correct interval display format (10 seconds is not 1 minute)

docs: Add guide for customizing system prompt

feat: Extract system prompt to .env for easy customization

feat: Add comprehensive system prompt for optimal Cursor AI execution

fix: Remove leftover code causing unreachable code error

docs: Add Cursor CLI mandatory requirement documentation

feat: Make Cursor CLI mandatory with setup validation

docs: Add comprehensive architecture summary

feat: Implement proper OS-level scheduling with --once mode

feat: Add Cursor CLI integration and comprehensive documentation

Migrate to Todoist API v1 with enhanced validation

Add Todoist API validation before starting scheduler

Change all user messages to English