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/options_flow.py

@@ -1,7 +1,6 @@
 """Options flow for NestQuest post-setup settings."""
 from __future__ import annotations
 
-import re
 from typing import Any
 
 import voluptuous as vol
@@ -33,18 +32,17 @@ from .const import (
     DEFAULT_UPDATE_INTERVAL,
     DOMAIN,
     MIN_UPDATE_INTERVAL,
+    TIME_PATTERN,
 )
 from .admin_allowlist import list_admin_ids, set_admin_ids
 
 MIN_HORIZON_DAYS = 1
 MIN_PANEL_IDLE_TIMEOUT = 30
 
-_TIME_PATTERN = re.compile(r"(?:[01]\d|2[0-3]):[0-5]\d")
-
 
 def _parse_time(value: str) -> bool:
     """Return True when value is a valid 24-hour HH:MM string."""
-    return _TIME_PATTERN.fullmatch(value) is not None
+    return TIME_PATTERN.fullmatch(value) is not None
 
 
 def _async_validate(user_input: dict[str, Any]) -> dict[str, str]: