Add Windows split tunneling

[ramimbo]

Closes #114

Summary

• add Windows settings for enabling split tunneling and selecting bypass apps
• capture the physical default route before tunnel startup, then add per-destination host routes for selected app processes
• apply the routing worker for both WireGuard and V2Ray connections and remove saved routes on disconnect

Tests

• PYTHONPATH=src python3 -m pytest -q
• python3 -m compileall -q src/cli src/conf src/helpers src/ui src/adapters src/typedef
• git diff --check HEAD~1 HEAD