fix(sensor): set state_class=None on static diagnostic metadata sensors

Four non-MONETARY diagnostic sensors had state_class set, causing HA
Recorder to add them to long-term statistics tables unnecessarily:

- home_size (m²):                   SensorStateClass.MEASUREMENT
- main_fuse_size (A):               SensorStateClass.MEASUREMENT
- number_of_residents:              SensorStateClass.MEASUREMENT
- estimated_annual_consumption(kWh):SensorStateClass.TOTAL

All four are static user metadata retrieved from Tibber's user API
(cached for 24 h, rarely or never changes in practice).  They carry no
time-series value: home_size and main_fuse_size don't change, and
estimated_annual_consumption is a rough Tibber estimate, not an actual
accumulating energy counter.

Setting state_class=None removes them from long-term statistics while
keeping normal state-change recording intact.

The three intentional non-None state_class values are unchanged:
- current_interval_price (MONETARY, TOTAL): Energy Dashboard
- current_interval_price_base (MONETARY, TOTAL): Energy Dashboard
- average_price_today (MONETARY, TOTAL): useful weekly/monthly trend

Impact: Reduced Recorder database growth; no user-visible sensor
behaviour change.

custom_components/tibber_prices/sensor/definitions.py

@@ -796,7 +796,7 @@ DIAGNOSTIC_SENSORS = (
         icon="mdi:ruler-square",
         entity_category=EntityCategory.DIAGNOSTIC,
         native_unit_of_measurement=UnitOfArea.SQUARE_METERS,
-        state_class=SensorStateClass.MEASUREMENT,
+        state_class=None,  # Static user metadata: no statistics useful
         entity_registry_enabled_default=False,
         suggested_display_precision=0,
     ),
@@ -807,7 +807,7 @@ DIAGNOSTIC_SENSORS = (
         entity_category=EntityCategory.DIAGNOSTIC,
         native_unit_of_measurement=UnitOfElectricCurrent.AMPERE,
         device_class=SensorDeviceClass.CURRENT,
-        state_class=SensorStateClass.MEASUREMENT,
+        state_class=None,  # Static user metadata: no statistics useful
         entity_registry_enabled_default=False,
         suggested_display_precision=0,
     ),
@@ -816,7 +816,7 @@ DIAGNOSTIC_SENSORS = (
         translation_key="number_of_residents",
         icon="mdi:account-group",
         entity_category=EntityCategory.DIAGNOSTIC,
-        state_class=SensorStateClass.MEASUREMENT,
+        state_class=None,  # Static user metadata: no statistics useful
         entity_registry_enabled_default=False,
         suggested_display_precision=0,
     ),
@@ -902,7 +902,7 @@ DIAGNOSTIC_SENSORS = (
         entity_category=EntityCategory.DIAGNOSTIC,
         native_unit_of_measurement=UnitOfEnergy.KILO_WATT_HOUR,
         device_class=SensorDeviceClass.ENERGY,
-        state_class=SensorStateClass.TOTAL,
+        state_class=None,  # Static Tibber estimate, not an actual accumulating counter
         suggested_display_precision=0,
     ),
     # Subscription data