perf(entity): scope availability subscription to the lock entities

[terafin]

Proposed change

The availability binary_sensor registers its state-change handler with all_states=True:

async_track_state_change_filtered(
    self.hass, TrackStates(True, set(), set()), self._handle_available_state_update
)

TrackStates(True, ...) subscribes to every state change in the entire Home Assistant instance. _handle_available_state_update then filters in Python and early-returns for any entity that isn't one of the slot's locks.

On a production instance with ~6–7 of these entities, cProfile measured the handler running ~86,580 times / 30s (~2,900/sec) and its inner generator ~640,100 times / 30s — the single largest application-level CPU consumer, doing no useful work.

Fix

Scope the subscription to just the lock entities:

TrackStates(False, {lock.lock.entity_id for lock in self.locks}, set())

self.locks is mutated at runtime (_handle_add_locks / _handle_remove_lock), so the tracked set is re-scoped via async_update_listeners() whenever locks change, and availability is recomputed at that point — previously the all-states firehose recomputed it implicitly, so this preserves behavior for the dynamic add/remove-lock case. The initial availability computation and the async_on_remove cleanup are unchanged.

Pure performance fix; no behavior change. Verified: the full test_binary_sensor.py, test_event.py, and test_callbacks.py suites pass (48 tests), and a new regression test asserts the subscription is scoped to the locks and re-scopes on lock add/remove.

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New feature (which adds functionality)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

Additional information

• Performance regression measured via cProfile on a production HA instance running 4.2.0.
• No existing issue; filing this PR directly.

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