feat: add global i18n configuration via CREWAI_I18N_FILE environment variable

- Add support for CREWAI_I18N_FILE environment variable to globally configure translation files
- Maintain backward compatibility with existing prompt_file parameter
- Priority order: explicit prompt_file > CREWAI_I18N_FILE env var > default en.json
- Add Chinese (zh.json) and Spanish (es.json) translation files for testing
- Add comprehensive tests covering environment variable functionality, priority handling, and error cases
- Resolves issue #3264 by providing global interface to change i18n files

Co-Authored-By: João <joao@crewai.com>

tests/utilities/test_i18n.py

@@ -1,3 +1,5 @@
+import json
+import os
 import pytest
 
 from crewai.utilities.i18n import I18N
@@ -42,3 +44,89 @@ def test_prompt_file():
     i18n.load_prompts()
     assert isinstance(i18n.retrieve("slices", "role_playing"), str)
     assert i18n.retrieve("slices", "role_playing") == "Lorem ipsum dolor sit amet"
+
+
+def test_global_i18n_file_environment_variable(monkeypatch):
+    """Test that CREWAI_I18N_FILE environment variable is respected"""
+    test_translations = {
+        "slices": {"role_playing": "Test role playing message"},
+        "tools": {"ask_question": "Test ask question message"}
+    }
+    
+    test_file_path = os.path.join(os.path.dirname(__file__), "test_env_prompts.json")
+    with open(test_file_path, "w", encoding="utf-8") as f:
+        json.dump(test_translations, f)
+    
+    try:
+        monkeypatch.setenv("CREWAI_I18N_FILE", test_file_path)
+        
+        i18n = I18N()
+        i18n.load_prompts()
+        
+        assert i18n.slice("role_playing") == "Test role playing message"
+        assert i18n.tools("ask_question") == "Test ask question message"
+        
+    finally:
+        if os.path.exists(test_file_path):
+            os.remove(test_file_path)
+
+
+def test_prompt_file_priority_over_environment_variable(monkeypatch):
+    """Test that explicit prompt_file takes priority over environment variable"""
+    monkeypatch.setenv("CREWAI_I18N_FILE", "/nonexistent/path.json")
+    
+    path = os.path.join(os.path.dirname(__file__), "prompts.json")
+    i18n = I18N(prompt_file=path)
+    i18n.load_prompts()
+    
+    assert i18n.retrieve("slices", "role_playing") == "Lorem ipsum dolor sit amet"
+
+
+def test_environment_variable_file_not_found(monkeypatch):
+    """Test proper error handling when environment variable points to non-existent file"""
+    monkeypatch.setenv("CREWAI_I18N_FILE", "/nonexistent/file.json")
+    
+    i18n = I18N()
+    with pytest.raises(Exception, match="Prompt file '/nonexistent/file.json' not found"):
+        i18n.load_prompts()
+
+
+def test_fallback_to_default_when_no_environment_variable(monkeypatch):
+    """Test that it falls back to default en.json when no environment variable is set"""
+    monkeypatch.delenv("CREWAI_I18N_FILE", raising=False)
+    
+    i18n = I18N()
+    i18n.load_prompts()
+    
+    assert isinstance(i18n.slice("role_playing"), str)
+    assert len(i18n.slice("role_playing")) > 0
+
+
+def test_chinese_translation_file():
+    """Test loading Chinese translation file"""
+    import os
+    
+    zh_path = os.path.join(os.path.dirname(__file__), "../../src/crewai/translations/zh.json")
+    zh_path = os.path.abspath(zh_path)
+    
+    i18n = I18N(prompt_file=zh_path)
+    i18n.load_prompts()
+    
+    assert i18n.retrieve("hierarchical_manager_agent", "role") == "团队经理"
+    assert i18n.slice("observation") == "\n观察:"
+    assert i18n.errors("tool_usage_error") == "我遇到了错误: {error}"
+
+
+def test_spanish_translation_file():
+    """Test loading Spanish translation file"""
+    import os
+    
+    es_path = os.path.join(os.path.dirname(__file__), "../../src/crewai/translations/es.json")
+    es_path = os.path.abspath(es_path)
+    
+    i18n = I18N(prompt_file=es_path)
+    i18n.load_prompts()
+    
+    assert i18n.retrieve("hierarchical_manager_agent", "role") == "Gerente del Equipo"
+    assert i18n.slice("observation") == "\nObservación:"
+    assert i18n.errors("tool_usage_error") == "Encontré un error: {error}"