water_purifier, range: drop invalid device_class='lock' from switches

SwitchDeviceClass only ever supported 'outlet'/'switch', not 'lock'.
switch.py passes desc.device_class straight to SwitchDeviceClass(...),
so any board with these hrefs raised ValueError during switch platform
setup and lost every switch entity for the device, not just the lock
ones (issue #349, TP2X_WATERPURIFIER_20K).

KIDS_LOCK_GENERIC/_VS_FALLBACK dodged this same bug (issues #181/#183)
by moving to a read-only BinarySensorDesc, but the water-purifier and
cooktop locks are genuinely writable, so they stay SwitchDesc and just
drop the invalid device_class (with an mdi:lock icon standing in for
the one entity_category=config gave them for free).

Added a registry-wide test that instantiates SwitchDeviceClass for
every SwitchDesc.device_class across every by_type registry, so a
future capability can't reintroduce the same crash.

tests/test_switch_device_class.py

@@ -0,0 +1,45 @@
+"""Guards against a SwitchDesc.device_class HA's SwitchDeviceClass doesn't
+recognize -- switch.py passes it straight to SwitchDeviceClass(...), and an
+invalid value raises out of the whole switch platform's async_setup_entry,
+taking down every switch entity for the device, not just the offending one
+(issue #349: water_purifier.py's lock switches used device_class='lock',
+which SwitchDeviceClass only ever supported as 'outlet'/'switch').
+
+Scans every by_type registry's declared capabilities rather than a specific
+fixture, so a new capability introducing the same mistake fails here instead
+of only surfacing as a live crash report.
+"""
+
+import importlib
+import pkgutil
+
+from homeassistant.components.switch import SwitchDeviceClass
+
+from custom_components.localthings.registry import by_type
+from custom_components.localthings.registry.entities import SwitchDesc
+
+
+def _all_registries():
+    for mod_info in pkgutil.iter_modules(by_type.__path__):
+        if mod_info.name.startswith("_"):
+            continue
+        mod = importlib.import_module(
+            f"custom_components.localthings.registry.by_type.{mod_info.name}"
+        )
+        reg = getattr(mod, "REGISTRY", None)
+        if reg is not None:
+            yield reg
+
+
+def test_every_switchdesc_device_class_is_valid_for_ha():
+    bad = []
+    for reg in _all_registries():
+        caps = [c for cs in reg.capabilities.values() for c in cs] + list(reg.pattern_capabilities)
+        for cap in caps:
+            for entity in cap.entities:
+                if isinstance(entity, SwitchDesc) and entity.device_class is not None:
+                    try:
+                        SwitchDeviceClass(entity.device_class)
+                    except ValueError:
+                        bad.append((reg.name, entity.key, entity.device_class))
+    assert bad == []