Gemini: add model fallback list and GEMINI_MODEL override to avoid 404 NOT_FOUND

demo_user.py

@@ -172,6 +172,16 @@ def generate_mermaid_from_image_gemini(base64_image):
     if not api_key:
         raise EnvironmentError("La clé API GEMINI_API_KEY n'est pas définie.")
 
+    model_from_env = os.environ.get("GEMINI_MODEL", "").strip()
+    model_candidates = [
+        model_from_env,
+        "gemini-2.0-flash",
+        "gemini-2.0-flash-lite",
+        "gemini-1.5-flash-latest",
+        "gemini-1.5-pro-latest",
+    ]
+    model_candidates = [m for m in model_candidates if m]
+
     try:
         client = genai.Client(api_key=api_key)
         prompt = """
@@ -188,21 +198,32 @@ def generate_mermaid_from_image_gemini(base64_image):
         - Inclus les relations les plus importantes seulement
         """
         
-        response = client.models.generate_content(
-            model="gemini-1.5-flash",
-            contents=[
-                types.Content(
-                    role="user",
-                    parts=[
-                        types.Part.from_text(text=prompt),
-                        types.Part.from_bytes(
-                            data=base64.b64decode(base64_image),
-                            mime_type="image/png",
-                        ),
+        last_error = None
+        response = None
+        for model_name in model_candidates:
+            try:
+                response = client.models.generate_content(
+                    model=model_name,
+                    contents=[
+                        types.Content(
+                            role="user",
+                            parts=[
+                                types.Part.from_text(text=prompt),
+                                types.Part.from_bytes(
+                                    data=base64.b64decode(base64_image),
+                                    mime_type="image/png",
+                                ),
+                            ],
+                        )
                     ],
                 )
-            ],
-        )
+                break
+            except Exception as e:
+                last_error = e
+                continue
+
+        if response is None:
+            raise last_error if last_error is not None else RuntimeError("Échec Gemini: aucune réponse")
 
         mermaid_code = (getattr(response, "text", None) or "").strip()
         if not mermaid_code: