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>

tests/test_api_admin_settings.py

@@ -13,7 +13,8 @@ proven against the DATABASE the routes wrote, not a parallel copy.
 Proven per the done-condition, everything read back through the API:
 
 - ``GET /api/v1/admin/settings`` returns the current effective settings
-  — the twelve documented fields at their defaults on a fresh database.
+  — the eleven documented fields at their defaults on a fresh database,
+  with no ``timezone_configured`` marker.
 - ``PATCH /api/v1/admin/settings`` PERSISTS the supplied fields and the
   NEXT read reflects them; a later partial update merges onto the
   current effective settings (omitted fields keep their stored value),
@@ -60,7 +61,7 @@ _dao_meta = importlib.import_module("nestquest_core.dao_meta")
 SETTINGS_META_KEY = "settings"
 
 #: The all-defaults effective settings a fresh database reports — the
-#: documented twelve fields, asserted literally so the payload contract is
+#: documented eleven fields, asserted literally so the payload contract is
 #: pinned here, independent of the core constants.
 DEFAULT_SETTINGS = {
     "horizon_days": 14,
@@ -74,7 +75,6 @@ DEFAULT_SETTINGS = {
     "end_of_day_report_enabled": True,
     "celebration_enabled": True,
     "timezone": "",
-    "timezone_configured": False,
 }
 
 
@@ -105,7 +105,7 @@ async def settings_client(temp_db_path: str) -> SimpleNamespace:
 async def test_get_settings_returns_defaults_on_a_fresh_database(
     settings_client: SimpleNamespace,
 ) -> None:
-    """GET returns the twelve documented fields at their defaults."""
+    """GET returns the eleven documented fields at their defaults."""
     response = await settings_client.client.get(
         "/api/v1/admin/settings", headers=_admin_headers()
     )
@@ -223,27 +223,38 @@ async def test_null_resets_a_field_to_its_default(
     assert reread.json()["horizon_days"] == 14
 
 
-async def test_timezone_configured_round_trips_with_an_explicit_empty_zone(
+async def test_default_settings_carry_no_timezone_configured_marker(
     settings_client: SimpleNamespace,
 ) -> None:
-    """An explicit empty (host-local) zone persists as configured.
+    """The removed auto-set marker is absent from the default response."""
+    response = await settings_client.client.get(
+        "/api/v1/admin/settings", headers=_admin_headers()
+    )
+    assert response.status_code == 200
+    assert "timezone_configured" not in response.json()
+    assert response.json()["timezone"] == ""
 
-    The admin clearing the zone PATCHes ``timezone: ""`` together with
-    ``timezone_configured: true``; the NEXT read — a reopened settings
-    screen — sees the marker, so the empty value is a persisted choice
-    rather than a fresh install to auto-set.
-    """
+
+@pytest.mark.parametrize("zone", ["America/New_York", ""])
+async def test_manual_timezone_patch_persists_and_is_returned(
+    settings_client: SimpleNamespace, zone: str
+) -> None:
+    """An admin's timezone PATCH is stored exactly as given and read back."""
     client = settings_client.client
-    fresh = await client.get("/api/v1/admin/settings", headers=_admin_headers())
-    assert fresh.json()["timezone_configured"] is False
+    seeded = await client.patch(
+        "/api/v1/admin/settings",
+        json={"timezone": "Europe/Dublin"},
+        headers=_admin_headers(),
+    )
+    assert seeded.status_code == 200
 
     patched = await client.patch(
         "/api/v1/admin/settings",
-        json={"timezone": "", "timezone_configured": True},
+        json={"timezone": zone},
         headers=_admin_headers(),
     )
     assert patched.status_code == 200
-    expected = {**DEFAULT_SETTINGS, "timezone_configured": True}
+    expected = {**DEFAULT_SETTINGS, "timezone": zone}
     assert patched.json() == expected
 
     reread = await client.get(
@@ -254,7 +265,43 @@ async def test_timezone_configured_round_trips_with_an_explicit_empty_zone(
         SETTINGS_META_KEY
     )
     assert raw is not None
-    assert json.loads(raw)["timezone_configured"] is True
+    stored = json.loads(raw)
+    assert stored["timezone"] == zone
+    assert "timezone_configured" not in stored
+
+
+async def test_timezone_configured_is_an_unknown_field(
+    settings_client: SimpleNamespace,
+) -> None:
+    """The removed marker is rejected like any unknown field; nothing is written."""
+    response = await settings_client.client.patch(
+        "/api/v1/admin/settings",
+        json={"timezone_configured": True},
+        headers=_admin_headers(),
+    )
+    assert response.status_code == 422
+    assert "timezone_configured" in str(response.json()["detail"])
+    raw = await _dao_meta.MetaStateDao(settings_client.database).get(
+        SETTINGS_META_KEY
+    )
+    assert raw is None
+
+
+async def test_stored_legacy_timezone_configured_key_is_ignored(
+    settings_client: SimpleNamespace,
+) -> None:
+    """A document written before the marker was removed still loads."""
+    await _dao_meta.MetaStateDao(settings_client.database).set(
+        SETTINGS_META_KEY,
+        json.dumps(
+            {"timezone": "America/Chicago", "timezone_configured": True}
+        ),
+    )
+    response = await settings_client.client.get(
+        "/api/v1/admin/settings", headers=_admin_headers()
+    )
+    assert response.status_code == 200
+    assert response.json() == {**DEFAULT_SETTINGS, "timezone": "America/Chicago"}
 
 
 # --- validation: rejected values never change the stored settings -------
@@ -273,8 +320,6 @@ async def test_timezone_configured_round_trips_with_an_explicit_empty_zone(
         ({"morning_summary_enabled": "yes"}, "morning_summary_enabled"),
         ({"celebration_enabled": 1}, "celebration_enabled"),
         ({"notify_target": 5}, "notify_target"),
-        ({"timezone_configured": "true"}, "timezone_configured"),
-        ({"timezone_configured": 1}, "timezone_configured"),
     ],
 )
 async def test_invalid_value_is_rejected_and_stored_settings_unchanged(