refactor(i18n): drop the vestigial descriptor name field

Since entity.py started routing named descriptors through the catalog
under desc.key, SamsungEntityDescription.name has been read for its
value nowhere -- only twice as a flag, to decide whether an entity was
translated at all. That left 148 English names duplicated between Python
and translations/en.json with nothing keeping them honest: six had
already drifted, invisibly, because editing the Python side changes
nothing a user sees.

So the field is gone, and translation_key defaults to desc.key. A
descriptor now sets translation_key only to share one catalog entry
across descriptors or to point at a differently-named one, and the
catalog is the only place an entity name exists.

Every descriptor resolves to exactly the translation key, icon, entity
category, enabled-default and gating it did before -- with one
deliberate exception: the hood fan, previously the sole descriptor with
no key at all, now resolves to 'fan'. That is inert, because fan.py sets
_attr_name = None so the entity presents as the device itself.

The three helpers that forwarded a name into a descriptor
(laundry.bool_option_switch, washer._bool_option_switch, air_purifier's
sensor table) lose that parameter. test_translations.py now requires a
catalog entry for every descriptor rather than only translated ones.

Claude-Session: https://claude.ai/code/session_01GiibJZZLWVvyxq7mc7EDNp

tests/test_select_options.py

@@ -89,7 +89,7 @@ async def test_unknown_vendor_option_round_trips_to_exact_raw_value():
             self.writes.append(value)
 
     desc = SelectDesc(
-        key='mode', name='Mode', translation_key='door_alert',
+        key='mode', translation_key='door_alert',
         options=('Known', 'FutureVendorMode'), write_fn=lambda *args: None,
     )
     capability = Capability(href='/x/vs/0', entities=(desc,))