Apply PR #144 review fixes: per-field settings fallback, strict validation, hardened AST scan (task 4dd8f870)

P2-1: replace the all-or-nothing from_options try/except in setup with
from_options_resilient, which falls back PER FIELD (logging a warning
naming the bad field) so a malformed sibling (e.g. morning_summary_time
'25:00') cannot silently reset horizon_days/day_rollover_time.
P2-2: drop _run_horizon_materialization's legacy horizon_days keyword and
branch; default settings to NestQuestSettings(); remove the legacy paragraph.
P2-3: _run_horizon_materialization now calls settings.horizon_window(today)
so the helper is real and shared; extend tests to run the integration path
(_run_horizon_materialization + _register_day_rollover_listener) with
horizon_days=3 / day_rollover_time='03:30'.
P2-4: harden the AST scan to forbid hass/config_entry names, .hass/.entry/
.config_entry and .config/.options/.data attributes, and getattr/hasattr
calls with those string args; add a negative-control test for each shape.
P2-5: __post_init__ is strict (rejects None for every field); the
None->default mapping lives ONLY in from_options via _option_value.
P3: remove dead shims (_day_rollover_hour_minute, _configured_horizon_days)
and repoint test_lifecycle at from_options; de-dup the two HH:MM
validators into one using a shared TIME_PATTERN in core/const; make
horizon_window's today required; reword the notify_target docstring to
not claim options-flow parity; document _option_value's None-as-absent
semantics; remove unused test helpers.

custom_components/nestquest/core/const.py

@@ -2,11 +2,19 @@
 from __future__ import annotations
 
 import logging
+import re
 
 DOMAIN = "nestquest"
 LOGGER_NAME = "custom_components.nestquest"
 LOGGER = logging.getLogger(LOGGER_NAME)
 
+#: Strict 24-hour ``HH:MM`` pattern shared by the options flow and the
+#: settings object's time validation, so a stored option and a freshly
+#: validated form submit parse the same way.  Defined here (HA-free) so
+#: both the integration's options flow and the core settings module
+#: import ONE pattern instead of re-copying it.
+TIME_PATTERN = re.compile(r"(?:[01]\d|2[0-3]):[0-5]\d")
+
 # Platforms set up per config entry (Feature 10): the per-child day
 # sensors and binary sensors.
 PLATFORMS: list[str] = ["sensor", "binary_sensor"]