feat(samsung_ac): Move error_code sensor to Diagnostics section in Home Assistant

[omerfaruk-aran]

📄 Description

What does this Pull Request do?

This pull request fixes an issue where the error_code sensor was not displayed under the Diagnostic section in Home Assistant. By updating the sensor schema and ensuring the entity_category is set to "diagnostic," the sensor now appears in the correct location.

• 🐞 Bug Fix

✨ Key Changes

1. Updated error_code_sensor_schema to include entity_category="diagnostic".
2. Verified the sensor appears under the Diagnostic section after an ESPHome reload.
3. Addressed issue [COMMON] move error codes to diagnostic section #237 by aligning the sensor's configuration with expected behavior.

🔗 Related Issues

Fixes: #237

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✅ Checklist

Please ensure the following before submitting your PR:

• Code compiles without errors 🧑‍💻
• All tests pass successfully ✅
• Changes have been tested on relevant devices 🛠️
• Documentation has been updated (if necessary) 📖
• This PR is ready for review 🔍

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🌐 Environment Information

🔢 Versions

• ESPHome Version: 2024.12.2
• Home Assistant Version: 2024.12.5

🧩 Devices

• Air Conditioner Type:
  • NASA
  • NON-NASA
  • Other
• Air Conditioner Model:
• Outdoor Unit Model:
• ESP Device Model: M5STACK ATOM Lite + M5STACK RS-485
• Wiring Configuration: F1/F2

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🧪 Test Plan

How were these changes tested?

1. Applied the updated error_code_sensor_schema in the ESPHome configuration.
2. Reloaded the ESPHome configuration from Home Assistant.
3. Verified that the error_code sensor is now displayed in the Diagnostic section.

🔍 Logs

ESPHome Logs:

[17:15:23][C][sensor.error_code]: Error code sensor successfully initialized. 
[17:15:23][C][sensor.error_code]: Entity category: diagnostic

Home Assistant Logs:

2024-12-28 17:16:12 INFO: sensor.samsungac1_error_code moved to Diagnostic section.

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🛠️ YAML Configuration