Add OneNote page date property option

[keilogic]

Summary

• add an opt-in OneNote importer setting to write page dates as Obsidian properties
• when enabled, imported notes get created and modified properties from Microsoft Graph page timestamps
• keep existing filesystem ctime/mtime preservation behavior unchanged

Refs #318.

Bounty / Payment Note

If this PR is accepted for the $150 attempt offer in #318, PayPal is available at https://www.paypal.com/paypalme/aogkft.

Testing

• git diff --check upstream/master...onenote-page-date-properties
• changed-file conflict-marker scan across the branch diff
• corepack pnpm build
• corepack pnpm test (32 tests passing)

[kepano]

This should be part of a single template feature across importers, see #609