Allow manually removing orphaned lock/gateway devices

[jbergler]

Summary

• A lock or gateway removed from the TTLock account drops out of the next get_locks()/get_gateways() call, but its device stays behind in HA's registry as an unavailable, entity-less orphan with no way to delete it.
• Implements async_remove_config_entry_device so the device can be manually deleted from HA's device page, guarded so a lock/gateway that's still active on the account can't be removed by mistake (it would just be recreated on the next reload).
• Applies to both lock and gateway devices. Missing runtime data (failed/unloaded entry) allows removal, since there's nothing to check against and that's plausibly when a user is pruning stale devices anyway.

Closes #114

Test plan

• script/check passes (lint, type-check, full suite)
• New tests cover: active lock blocked, orphaned lock allowed, active gateway blocked, missing entry data allowed
• Manual verification in a live HA instance (not done — no real TTLock account in this environment)

🤖 Generated with Claude Code

https://claude.ai/code/session_01Qps3xgXbFK1fcxd4ZeRgZY

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.02%. Comparing base (18c9ad6) to head (c0dd0c1).
✅ All tests successful. No failed tests found.

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #318      +/-   ##
===========================================
+ Coverage    96.00%   96.02%   +0.02%     
===========================================
  Files           17       17              
  Lines         1602     1611       +9     
===========================================
+ Hits          1538     1547       +9     
  Misses          64       64              

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