Improve error handling in Quay client HTTP requests

[fao89]

This enhances error reporting when external Quay.io API requests fail by checking HTTP response status before attempting JSON parsing.

Changes:

• Add status code validation in manifest.rs before JSON deserialization
• Add status code validation in tag.rs before JSON deserialization
• Return clear error messages with HTTP status codes
• Prevent confusing "JSON parsing" errors when getting HTML error pages

This improves debugging by showing actual HTTP errors (e.g., "403 Forbidden") instead of cryptic "expected value at line 1 column 1" JSON parsing failures.

Network tests now fail properly with actionable error messages when external services have authentication or permission issues.

🤖 Generated with Claude Code

Co-Authored-By: Claude Sonnet 4 [email protected] Signed-off-by: Fabricio Aguiar [email protected]

rh-pre-commit.version: 2.3.2 rh-pre-commit.check-secrets: ENABLED