Fixed bug where proof of payment download links used raw locationID instead
of shareID (locationID + checksum), causing link validation to fail. Added
AsyncLink component to handle async shareID generation gracefully.
Changes:
- BillEditForm: Generate shareID using generateShareId server action
- BillEditForm: Use AsyncLink to prevent broken links during async load
- AsyncLink: New reusable component for links that need async data
- Updated download URL from locationID-billID to shareID-billID format
Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>
