Backend CI tests on Python 3.12 and 3.14, with the extras installed

A matrix of the declared floor and the newest release in place of 3.13
alone. The job now syncs --all-extras like `make test-backend`, since the
mail, MQTT and Influx tests fail on a fresh venv without the server extra.
Both packages list 3.14 among their classifiers.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WgBfkm4rCmtd1T4vHWjEPx

worker/pyproject.toml

@@ -17,6 +17,7 @@ classifiers = [
     "Programming Language :: Python :: 3",
     "Programming Language :: Python :: 3.12",
     "Programming Language :: Python :: 3.13",
+    "Programming Language :: Python :: 3.14",
     "Topic :: Home Automation",
     "Topic :: Scientific/Engineering",
     "Topic :: System :: Distributed Computing",