v1.15.7: CI maintenance release

v1.15.7 — CI maintenance release

No functional changes. This release exists to produce a green CI badge on a release tag; the integration behaviour is identical to v1.15.6.

What was fixed (CI only)

The CI jobs had been failing since the test-suite modernisation because of three environment-specific issues that did not reproduce on a Windows development machine:

1. Descriptor sample files were tracked in Git with UPPERCASE filenames (BIV.XML, FVE.XML, FVEINV.XML, OKRUH.XML, SPOT.XML, STAVJED.XML, TUV1.XML) while the test code referenced them in lowercase. On Windows's case-insensitive filesystem this worked; on the case-sensitive Linux runners it failed with FileNotFoundError. Renamed the seven files in Git to lowercase to match the repo convention (descriptors lowercase, data files uppercase).

2. lxml was not in requirements-dev.txt. The xcc integration imports lxml at module load, and without it the Home Assistant test job failed at collection with ModuleNotFoundError: No module named 'lxml'. Added lxml>=4.6.0 and aiofiles>=0.8.0 (both are manifest runtime deps) to the dev requirements.

3. Latent import/path bugs in HA-only tests that were previously masked by the lxml collection failure: test_friendly_names_fix.py missing import os, test_number_switch_values.py missing import sys and the project_root Path definition, plus stale UPPERCASE descriptor references in test_specific_entity_translations.py and test_czech_english_translations.py.

Upgrade notes

If you're on v1.15.6 there is no reason to upgrade — this release contains no functional changes, only CI/test-infrastructure fixes. It is tagged so the release badge reflects the repaired workflow.