[FE-95] Asset photo gallery with drag-and-drop ordering

[yusuftomilola]

Overview

@dnd-kit (core, sortable, modifiers, utilities) is installed but unused. Photos matter for asset identification and condition records, and ordering them is a natural drag-and-drop use case.

Tasks

• Add a photo gallery to the asset detail page with multi-file upload via react-dropzone.
• Support drag-to-reorder with @dnd-kit/sortable, persisting the order.
• Let the user set a primary image used as the thumbnail in list views.
• Add a lightbox for full-size viewing with keyboard navigation.
• Delete with confirmation; show upload progress and per-file errors.
• Use next/image with correct sizing and lazy loading.
• Ensure drag-and-drop has a keyboard-accessible alternative — @dnd-kit supports this, but it must be wired up.

Acceptance Criteria

• Photos upload, reorder, and persist their order.
• The primary image appears as the thumbnail in the assets list.
• Reordering is achievable by keyboard alone.

Dependencies

Backend from [BE-90] and [BE-106].

Notes for Contributors

Comment below to be assigned.