feat: Add LOCAL variable support for responses with UTF-8 JSON encoding.

Description: This feature adds support for UTF-8 encoding in JSON responses, allowing for proper handling of special characters and emojis.

- Implement unit tests for UTF-8 encoding in various model providers including Gemini, OpenAI, and OpenAI Compatible.
- Validate UTF-8 support in token counting, content generation, and error handling.
- Introduce tests for JSON serialization ensuring proper handling of French characters and emojis.
- Create tests for language instruction generation based on locale settings.
- Validate UTF-8 handling in workflow tools including AnalyzeTool, CodereviewTool, and DebugIssueTool.
- Ensure that all tests check for correct UTF-8 character preservation and proper JSON formatting.
- Add integration tests to verify the interaction between locale settings and model responses.

.env.example

@@ -108,3 +108,9 @@ MAX_CONVERSATION_TURNS=20
 # ERROR: Shows only errors
 LOG_LEVEL=DEBUG
 
+# Optional: Language/Locale for AI responses
+# When set, all AI tools will respond in the specified language
+# while maintaining their analytical capabilities
+# Examples: "fr-FR", "en-US", "zh-CN", "zh-TW", "ja-JP", "ko-KR", "es-ES"
+# Leave empty for default language (English)
+# LOCALE=fr-FR