Feature Request: Implement Category Discovery Command

Related Roadmap Section

This issue addresses the following items from ROADMAP.md:

• Priority 2.3: Category & Language Discovery -> List available categories from API
• API Endpoints: GET /api/v1/categories/
• Proposed Command: corpus-client categories

The Problem

Currently, users have no way to view the available upload categories directly from the terminal. Because the backend requires specific Category IDs (UUIDs) for successful file uploads, users must either guess or manually look them up elsewhere, causing friction and potential upload errors.

Proposed Solution

Implement the corpus-client categories command to act as a live reference menu.

Requirements:

• Require user authentication before making the request.
• Fetch the live list of categories from /api/v1/categories/.
• Parse the JSON response safely.
• Display the results (ID and Name) in a readable, formatted terminal table using the rich library.