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.

locales/languages.json

@@ -1,11 +1,11 @@
 {
   "zh": {
     "label": "中文",
-    "llmInstruction": "请使用中文回答。"
+    "llmInstruction": "重要：你必须使用中文撰写所有内容。请使用中文回答。"
   },
   "en": {
     "label": "English",
-    "llmInstruction": "Please respond in English."
+    "llmInstruction": "IMPORTANT: You MUST write ALL content exclusively in English. Do NOT use any other language in your response."
   },
   "es": {
     "label": "Español",
@@ -29,6 +29,6 @@
   },
   "th": {
     "label": "ไทย",
-    "llmInstruction": "กรุณาตอบเป็นภาษาไทย"
+    "llmInstruction": "IMPORTANT: You MUST write ALL content exclusively in Thai language (ภาษาไทย). Do NOT use any other language in your response. กรุณาตอบเป็นภาษาไทยเท่านั้น ห้ามใช้ภาษาอื่น"
   }
-}
+}