Print human-readable error messages with suggestions when API calls fail

[Copilot]

API failures surfaced raw HTTP exceptions (e.g. HTTPError: 500 Server Error) with no context or guidance. This adds human-readable error messages and actionable suggestions for common failure modes.

Changes

• settings.py (new): HTTP_ERROR_MAP — maps HTTP status codes to (display_text, suggestion) tuples covering 400, 401, 403, 404, 409, 422, 429, 500, 503 with targeted suggestions (e.g. quota, project, auth)
• utils/http.py: BaseConnection.request() catches HTTPError and re-raises with a composed message — applies to all endpoints (Materials, Workflows, Jobs)

Example

Before:

HTTPError: 500 Server Error: Internal Server Error for url: .../jobs/id/submit

After:

Error 500: Internal Server Error. An error occurred on the server. Contact support if the problem persists.

# 403 example
Error 403: Forbidden. You do not have permission to access this resource. Set the correct project or check your account permissions.

# 429 example
Error 429: Too Many Requests. You have exceeded your quota. Update your quota or try again later.

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