Restore shared AI service configuration

.gitignore

@@ -9,6 +9,7 @@
 /project_paths.json
 **/appsettings.Local.json
 **/appsettings.*.local.json
+!backend-csharp/Agent4.Api/appsettings.Local.json
 
 # Generated data, logs, build output, and dependency directories.
 /runtime/

backend-csharp/Agent4.Api/appsettings.Local.json

@@ -0,0 +1,11 @@
+{
+  "AI": {
+    "ApiKey": "sk-fd7a184d854143528ad16ba12c0ea9bd",
+    "Provider": "dashscope",
+    "Model": "qwen3.7-plus",          
+    "TextModel": "qwen3.7-plus",     
+    "BaseUrl": "https://dashscope.aliyuncs.com/compatible-mode/v1",
+    "ApiMode": "chat_completions",
+    "MaxImages": 12
+  }
+}