Soft delete with undo

[byteofhoney]

Goal:

Make deleting a snippet reversible for a short window instead of permanent.

User story:

As a user, I want an undo option after deleting so that I don't lose a snippet by mistake.

Tasks

• Replace hard delete with a deleted: true flag on the snippet document
• Update index() query to exclude deleted: true snippets by default
• Flash message includes an "Undo" action for a short window after deletion
• Undo action clears the deleted flag and restores the snippet

Acceptance Criteria

• Deleting a snippet removes it from the grid immediately
• Clicking "Undo" within the time window restores it fully, unchanged
• After the window expires, the snippet stays hidden (permanent cleanup can be a separate feature)