Prioritize Mistral AI for AI agent requests and update default models

Reorders AI provider priority to favor Mistral, updates default models to Mistral variants, and adjusts client initialization logic in `ai_agent.py`.

Replit-Commit-Author: Agent
Replit-Commit-Session-Id: 923ae0e3-a363-4db8-b04a-e8baca2a1330
Replit-Commit-Checkpoint-Type: full_checkpoint
Replit-Commit-Event-Id: 1d6be57f-2086-4267-b6c2-1439250ce53e
Replit-Commit-Screenshot-Url: https://storage.googleapis.com/screenshot-production-us-central1/8af7d2ec-2cc3-4ece-8af3-9f071488d072/923ae0e3-a363-4db8-b04a-e8baca2a1330/AOIftG8
Replit-Helium-Checkpoint-Created: true

artifacts/flask-api/ai_agent.py

@@ -18,23 +18,20 @@ _client: OpenAI | None = None
 def get_client() -> OpenAI:
     """
     Supporte trois modes (par ordre de priorité) :
-    1. Replit AI Integration : AI_INTEGRATIONS_OPENAI_BASE_URL + AI_INTEGRATIONS_OPENAI_API_KEY
-    2. Mistral AI            : MISTRAL_API_KEY (+ MISTRAL_BASE_URL optionnel)
-    3. OpenAI standard       : OPENAI_API_KEY (+ OPENAI_BASE_URL optionnel)
+    1. Mistral AI            : MISTRAL_API_KEY (+ MISTRAL_BASE_URL optionnel)
+    2. OpenAI standard       : OPENAI_API_KEY (+ OPENAI_BASE_URL optionnel)
+    3. Replit AI Integration : AI_INTEGRATIONS_OPENAI_BASE_URL + AI_INTEGRATIONS_OPENAI_API_KEY
     """
     global _client
     if _client is None:
-        replit_base = os.environ.get("AI_INTEGRATIONS_OPENAI_BASE_URL")
-        replit_key  = os.environ.get("AI_INTEGRATIONS_OPENAI_API_KEY")
         mistral_key  = os.environ.get("MISTRAL_API_KEY")
         mistral_base = os.environ.get("MISTRAL_BASE_URL", MISTRAL_BASE_URL)
         std_key      = os.environ.get("OPENAI_API_KEY")
         std_base     = os.environ.get("OPENAI_BASE_URL")
+        replit_base  = os.environ.get("AI_INTEGRATIONS_OPENAI_BASE_URL")
+        replit_key   = os.environ.get("AI_INTEGRATIONS_OPENAI_API_KEY")
 
-        if replit_base and replit_key:
-            logger.info("Utilisation de l'intégration Replit AI")
-            _client = OpenAI(base_url=replit_base, api_key=replit_key)
-        elif mistral_key:
+        if mistral_key:
             logger.info("Utilisation de l'API Mistral AI (%s)", mistral_base)
             _client = OpenAI(base_url=mistral_base, api_key=mistral_key)
         elif std_key:
@@ -43,6 +40,9 @@ def get_client() -> OpenAI:
             if std_base:
                 kwargs["base_url"] = std_base
             _client = OpenAI(**kwargs)
+        elif replit_base and replit_key:
+            logger.info("Utilisation de l'intégration Replit AI")
+            _client = OpenAI(base_url=replit_base, api_key=replit_key)
         else:
             raise RuntimeError(
                 "Aucune clé IA configurée. "