Tests compare against Home Assistant's date, and 1.15.1

[AboveColin]

Three usage tests failed every day between midnight UTC and midnight in US/Pacific. This fixes the tests and releases 1.15.1. The integration code does not change.

Cause

tests/test_ai_task.py and tests/test_init.py built the expected day with date.today(), which is the system date. The integration uses Home Assistant's clock, and the test harness sets it to US/Pacific. When the two dates differ, the tests fail:

• test_what_the_task_spends_lands_in_the_day_s_usage: date(2026, 9, 22) == date(2026, 9, 23) fails.
• test_yesterdays_total_does_not_count_against_today: '101' == '2' fails. The stored "yesterday" was today for Home Assistant.
• test_a_spent_budget_skips_the_probe_and_still_says_so.

The tests now use dt_util.now().date().

Gate

Run at 05:30 in Europe/Amsterdam, inside the window where main fails.

Check	main	this branch
test_ai_task.py + test_init.py, TZ=Europe/Amsterdam	3 failed	67 passed
same, TZ=UTC	3 failed	67 passed
same, TZ=America/Los_Angeles	67 passed	67 passed
same, TZ=Pacific/Kiritimati	not run	67 passed
ruff check, ruff format --check		pass
mypy --strict		no issues in 20 source files
pytest		407 passed, 12 skipped, 97% coverage, config_flow.py 100%
mkdocs build --strict, hassfest		pass, 0 invalid integrations