v0.1.16 Beta

Beta build for private distribution.

• Redesigned student roster editor: inline editing, range selection, per-row
  delete, and spreadsheet paste.
• CSV roster import can update existing students, not just add them.
• Capture student email addresses; mark students as "Inactive" to skip them
  during provisioning.
• New Feedback and bug-report buttons in the sidebar.
• Fixes to provisioning flow, assignment card layout, and perceived
  navigation speed.