US4.3: File Upload & Storage

[urbantech]

As a user,
I want to upload and manage files (e.g., images, documents) for my projects,
So that I can include them in my app.

Acceptance Criteria:

1. Backend:
   • POST /api/projects/:id/files - Upload a file (max 10MB).
   • GET /api/projects/:id/files - List all files for a project.
   • GET /api/projects/:id/files/:fileId - Download a file.
   • DELETE /api/projects/:id/files/:fileId - Delete a file.
2. Storage:
   • Files stored in uploads/project-{id}/ (local) or cloud storage (S3-compatible).
   • File metadata in files table: id, project_id, filename, path, mimetype, size, created_at.
3. Frontend:
   • FileUpload.jsx - Drag-and-drop or file picker.
   • FileList.jsx - Display files with previews (if images) and delete options.
4. Security:
   • Only project owners can upload/delete files.
   • File type restrictions (e.g., no .exe).