Fix thermostat rounding and Sinope polling idempotency

[dmulcahey]

Converting a requested thermostat setpoint with int(value * 100) can lose a centidegree to floating-point representation (for example, 19.9 becomes 1989). Use round() for heating/cooling and occupied/away setpoints, with positive and negative precision coverage.

Sinope time updates also need one task across repeated enable/disable calls. Keep ownership until cancellation finishes, restart only if re-enabled, and prevent restarts after entity removal. Lifecycle tests cover repeated enable, rapid disable/re-enable, and removal while cancellation is pending.

Supersedes #688.

Validation against dev at 66603431339afe37fa0048b70ff31d77dceb8f95: Python 3.12 full suite, 1384 passed, coverage above the 95% project gate; full pre-commit (codespell, Ruff, formatting, mypy, lock check) passed. Relevant regression checks fail on the unchanged base. GitHub CI for Python 3.12/3.13/3.14 is reported separately on the PR.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.20%. Comparing base (6660343) to head (c31c6f0).

Additional details and impacted files

@@           Coverage Diff           @@
##              dev     #830   +/-   ##
=======================================
  Coverage   97.19%   97.20%           
=======================================
  Files          57       57           
  Lines       10560    10573   +13     
=======================================
+ Hits        10264    10277   +13     
  Misses        296      296           

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