Fix thermal comfort calculations, sensor lifecycle, and Chinese localization

[blakebill]

Summary

This PR improves calculation correctness and sensor lifecycle handling, while completing the Simplified and Traditional Chinese localization.

Changes

Reliability and correctness

• Correct the winter Scharlau formula by restoring the quadratic humidity term.
• Mark calculated sensors unavailable when their temperature or humidity source is missing, unavailable, or invalid.
• Handle invalid temperature conversion without leaving stale calculated values.
• Enable all calculated sensors by default for config entries created in basic mode, while preserving advanced sensor selections.
• Clean up state-change and polling listeners when an entry or YAML entity is unloaded.
• Prevent per-entity names, icons, and enablement settings from mutating shared sensor descriptions.
• Keep existing configuration entries editable when a configured source entity is temporarily missing or has been removed.

Localization

• Complete the Simplified Chinese (zh-Hans) translation.
• Add complete Traditional Chinese (zh-Hant) support.
• Standardize thermal index names, temperature terminology, comfort levels, and risk labels.
• Synchronize the Inlang language configuration with the available translation files.
• Remove the obsolete standalone Estonian sensor translation fragment.

Tests

• Add regression coverage for the corrected winter Scharlau boundaries.
• Add coverage for default entity enablement, listener cleanup, unavailable sources, shared description isolation, and missing source entities in the options flow.
• Restore collection of previously misnamed sensor tests.

Validation

• Translation JSON files parse successfully
• Simplified and Traditional Chinese keys match the English source
• git diff --check passes