Remove every automatic timezone-setting mechanism (task 7f685179)

The application timezone is now only ever set by an admin saving it:

- API: drop adopt_reported_timezone; the panel household clock reads the
  stored settings only and ignores any timezone request header.
- Integration: stop reporting Home Assistant's time_zone in an
  X-NestQuest-Timezone header (snapshot, completion and SSE requests).
- Admin app: remove the browser-zone detection and the automatic PATCH
  on load; the timezone field stays a manual control.
- Remove the timezone_configured marker from the core settings, the
  settings store and the admin settings API. A stored document that
  still carries the key loads harmlessly (unknown keys are ignored).

Tests replace the adoption expectations with proofs that a panel
timezone header never changes the stored settings, a fresh install's
empty zone stays empty with no settings write, the admin settings carry
no timezone_configured, and a manual admin timezone PATCH persists.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

custom_components/nestquest/core/settings.py

@@ -49,7 +49,6 @@ from .const import (
     CONF_MORNING_SUMMARY_TIME,
     CONF_NOTIFY_TARGET,
     CONF_TIMEZONE,
-    CONF_TIMEZONE_CONFIGURED,
     DEFAULT_AFTERNOON_REMINDER_TIME,
     DEFAULT_AUTOMATION_ENABLED,
     DEFAULT_DAY_ROLLOVER_TIME,
@@ -57,7 +56,6 @@ from .const import (
     DEFAULT_HORIZON_DAYS,
     DEFAULT_MORNING_SUMMARY_TIME,
     DEFAULT_TIMEZONE,
-    DEFAULT_TIMEZONE_CONFIGURED,
     LOGGER,
     TIME_PATTERN,
 )
@@ -243,12 +241,6 @@ _FIELDS: tuple[tuple[str, str, Any, Callable[[Any], Any]], ...] = (
         _resolve_bool,
     ),
     ("timezone", CONF_TIMEZONE, DEFAULT_TIMEZONE, _resolve_timezone),
-    (
-        "timezone_configured",
-        CONF_TIMEZONE_CONFIGURED,
-        DEFAULT_TIMEZONE_CONFIGURED,
-        _resolve_bool,
-    ),
 )
 
 
@@ -279,10 +271,6 @@ class NestQuestSettings:
     end_of_day_report_enabled: bool = DEFAULT_AUTOMATION_ENABLED
     celebration_enabled: bool = DEFAULT_AUTOMATION_ENABLED
     timezone: str = DEFAULT_TIMEZONE
-    #: ``True`` once the admin explicitly chose :attr:`timezone` (even
-    #: the empty host-local value); ``False`` on a fresh install, where
-    #: the admin UI may auto-set the browser's zone.
-    timezone_configured: bool = DEFAULT_TIMEZONE_CONFIGURED
 
     def __post_init__(self) -> None:
         # Validate STRICTLY at construction so a hand-built instance
@@ -315,7 +303,6 @@ class NestQuestSettings:
             "afternoon_reminder_enabled",
             "end_of_day_report_enabled",
             "celebration_enabled",
-            "timezone_configured",
         ):
             value = getattr(self, name)
             if not isinstance(value, bool):