Add Apple permission probing during setup

[priyanshujain]

Summary

• Add lightweight CheckPermission() and CheckAppleContactsPermission() probe functions that trigger macOS TCC permission dialogs with a minimal osascript call (not a full sync)
• Show the user a message before the permission dialog appears, and handle denial gracefully with clear instructions
• Add Apple Contacts as a new source option in the obk setup wizard
• Add integration tests for both permission probes

Test plan

• go build ./... passes
• go test ./source/applenotes/... ./source/contacts/... passes
• On macOS, run go test -tags "darwin,integration" ./source/applenotes/... ./source/contacts/... to verify probes
• Manual test: run obk setup, select Apple Notes and Apple Contacts, verify permission dialogs appear with context messages