feat(registry): route AVT-WW-TP1-23 air purifier boards (#190)

AVT-WW-TP1-23-AXX500 (AX053B810HGD) reported device_type 'unknown' with
empty oneUiVersion, falling back to common caps. It's the same BESPOKE
Cube Air lineage as A-VTWW-TP2-21-COMMON (issue #151), just with the
'-WW-' delimiter shifted one letter left ('A-VTWW-' -> 'AVT-WW-'), which
splits into an 'AVT'/'WW' token pair the existing whole-token 'VTWW' entry
can't see. Added 'AVT' as its own board token onto the same air_purifier
registry -- the resource surface (wind/strength fan, HEPA filter, air
quality sensors, alarms) already matched with zero unbound hrefs once
routed there, so no new capabilities were needed.

custom_components/localthings/registry/by_type/__init__.py

@@ -87,6 +87,12 @@ _BOARD_TOKEN_TO_KEY: dict[str, str] = {
     'DHM': 'dehumidifier',          # issue #88 -- target humidity, no climate
     'TVTL': 'air_purifier',         # issue #56 (ARTIK051)
     'VTWW': 'air_purifier',         # issue #151 (BESPOKE Cube Air)
+    'AVT': 'air_purifier',          # issue #190 -- AVT-WW-TP1-23-AXX500, a
+                                     # next-gen BESPOKE Cube Air board; same
+                                     # lineage as VTWW above but the '-WW-'
+                                     # delimiter now falls one letter to the
+                                     # left ('A-VTWW-' -> 'AVT-WW-'), splitting
+                                     # into a token the existing entry can't see
     'AIR': 'air_purifier',          # issue #130 (TP1X_DA-AC-AIR)
     'WATERPURIFIER': 'water_purifier',   # issue #90
     'ADW': 'dishwasher',

custom_components/localthings/registry/by_type/air_purifier.py

@@ -16,6 +16,11 @@ match_fn discriminators that keep them from colliding):
   token, added for it. Its fan
   is WIND_STRENGTH_FAN on /wind/strength/vs/0 rather than FAN on
   /mode/vs/0 -- see that capability's comment.
+- AVT-WW-TP1-23-class (issue #190). A next-gen board in the same VTWW
+  lineage, resolved via its own 'AVT' board token since the '-WW-' delimiter
+  falls one letter to the left of 'VTWW's whole-token spelling. Same
+  resource surface as A-VTWW-TP2-21-COMMON above; no new capabilities
+  needed.
 
 Reuses dishwasher.DIAGNOSIS for /diagnosis/vs/0 (identical field/write
 contract).