fix: 3 fixes for Step 2, Step 4, Step 5

1. Step 5: Use empty model_config_dict={} so camel-ai doesn't spread
   api_key into create() - AsyncOpenAI reads env vars automatically.
   Step 3 unaffected (same env vars, just cleaner ModelFactory call).

2. Step 2: Fix Thai text truncation - isalnum() stripped Thai chars.
   Use re.sub(r'[^\w]', '', username, re.UNICODE) instead.

3. Step 4: Move get_language_instruction() to START of prompt (not end)
   and strengthen wording with MUST/IMPORTANT prefix.

backend/scripts/run_parallel_simulation.py

@@ -1032,18 +1032,13 @@ def create_model(config: Dict[str, Any], use_boost: bool = False):
     print(f"{config_label} model={llm_model}, base_url={llm_base_url[:40] if llm_base_url else '默认'}...")
     
     # camel-ai reads OPENAI_API_KEY from env automatically
-    # Pass api_key and base_url via model_config_dict
-    # camel-ai extracts these for the OpenAI client constructor
-    model_config = {}
-    if llm_api_key:
-        model_config["api_key"] = llm_api_key
-    if llm_base_url:
-        model_config["base_url"] = llm_base_url
+    # AsyncOpenAI reads OPENAI_API_KEY and OPENAI_BASE_URL from env automatically
+    # Pass empty model_config_dict so nothing is spread to create() call
     
     return ModelFactory.create(
         model_platform=ModelPlatformType.OPENAI,
         model_type=llm_model,
-        model_config_dict=model_config,
+        model_config_dict={},
     )