fix: fix favorites command not working

[ingjieye]

Summary

• Fix xhs favorites failing when the current web signing flow rejects the direct API request
• Update the favorites request parameters to match the current web API shape
• Use the existing Camoufox browser fallback in this project to capture the real web API response when signed requests fail
• Wrap Camoufox startup and page-driving failures in project-level exceptions
• Add regression tests for request parameters, fallback triggers, Camoufox backend usage, and fallback failure handling

Verification

• uv run --extra dev ruff check xhs_cli/client_mixins.py tests/test_client.py
• uv run --extra dev pytest -q
• uv run xhs favorites --json

Notes

• The browser fallback uses the existing Camoufox runtime in this project and does not hard-code a local Chrome executable path.