fix: notification list returns HTTP 500

[q-soriarty]

Problem

`copia-cli notification list` fails with `Error: API error (HTTP 500)`.

Root cause

The Copia/Gitea server returns 500 on the notifications endpoint. This may be:

1. A server-side bug in Copia's Gitea instance
2. An incorrect API endpoint path
3. Missing required query parameters

Affected commands

• `notification list`
• Potentially `notification read`

Investigation needed

1. Verify the correct Gitea notification endpoint: `GET /api/v1/notifications`
2. Check if the endpoint requires specific query parameters
3. Test directly via `copia-cli api /notifications` to isolate

Discovered by

Real-world testing of installed rpm package.

[github-actions]

Closed by #124 (merged into develop).