feat: Add Board ID filtering to list endpoint and Copy Board ID feature.

[LordNayan]

This PR adds the ability to filter boards by ID in the list endpoint and provides a UI feature to easily copy board IDs for use in external integrations.

Changes

Backend (api)

• boards.controller.ts: Modified listBoards to accept optional boardID parameter

  • When boardID is provided, returns only that specific board as a single-element array
  • When omitted, returns all boards (existing behavior unchanged)

• validate.middleware.ts: Updated boardListSchema to accept optional boardID field

Frontend (web)

• AdminBoardsPage.tsx: Added "Copy Board ID" button in the actions column
  • Clipboard icon button for each board row
  • Shows green checkmark confirmation after copying
  • Toast notification on success/failure