fix(climate): keep optimistic state until DKN cloud catches up

The DKN cloud REST endpoint lags behind the unit for several seconds
after a write, even though the unit itself and the DKN app reflect
the change immediately. The previous 2.5s optimistic-overlay TTL
expired well before the cloud caught up, so the next coordinator
publish (REST poll or socket device-data push) carried stale values
and the HA UI reverted to the previous setting.

Extend the overlay TTL to 30s as a safety bound, and track the
underlying device key + expected device value alongside each overlay.
On every coordinator publish, clear overlays whose device key now
reports the expected value (cloud has confirmed). The TTL still
caps how long a silently-failed write can hold a wrong value.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

custom_components/dkncloudna/const.py

@@ -39,9 +39,11 @@ DEFAULT_SCAN_INTERVAL = 60  # seconds
 MIN_SCAN_INTERVAL = 30
 MAX_SCAN_INTERVAL = 300
 
-# Optimistic overlay: how long to hold a locally-set value before trusting
-# the next coordinator refresh. Must exceed the write→cloud→poll round-trip.
-OPTIMISTIC_TTL_SEC: float = 2.5
+# Optimistic overlay: safety bound for cloud-propagation lag. Overlays
+# normally clear earlier via reconciliation once the device echoes the
+# requested value; this TTL guarantees the UI cannot get stuck on a
+# locally-set value indefinitely if the write was silently rejected.
+OPTIMISTIC_TTL_SEC: float = 30.0
 
 # Post-write coordinator refresh: coalesced delay after a device command.
 POST_WRITE_REFRESH_DELAY_SEC: float = 1.0