Add comprehensive test coverage for routes and nodes
Tests cover:
- routes.py: Input validation, path traversal protection, JSON
error handling, GUID sanitization (12 new tests)
- nodes/ideogram4_nodes.py: Prompt assembly, bbox normalization,
palette handling, JSON serialization, input coercion (28 new tests)
All tests use mocks via conftest.py to avoid ComfyUI dependencies.
Tests import the repo as a proper package so routes.py relative
imports work unchanged.
CI: Install aiohttp for route tests.
Co-authored-by: Cursor Agent <cursoragent@cursor.com>