feat(llm): hide api_key from all API responses and document max_tokens as reserved

Security Enhancement:
   - API keys are now always filtered to null in all LLM config API responses
   - Created LLMModelConfigDataWithoutSecret schema for response validation
   - Added _filter_api_key_from_config() helper in API routes
   - Modified repository to always hide api_key in get_user_effective_configs()
   - Update/create operations still accept and store api_key securely

   Documentation Updates:
   - Updated API key visibility section to reflect new security policy
   - Updated all response examples to show api_key as null
   - Marked max_tokens field as reserved for future use
   - Added "Reserved Fields" section explaining unused fields

   This defense-in-depth approach prevents API keys from being leaked through
   logs, browser devtools, or network monitoring.

gns3server/api/routes/controller/llm_model_configs.py

@@ -41,6 +41,21 @@ log = logging.getLogger(__name__)
 
 router = APIRouter()
 
+
+def _filter_api_key_from_config(config: dict) -> dict:
+    """
+    Remove API key from config dict for security.
+    API keys should NEVER be returned via API endpoints.
+
+    :param config: Configuration dictionary
+    :return: Configuration dictionary with api_key set to None
+    """
+    filtered = config.copy()
+    if "api_key" in filtered:
+        filtered["api_key"] = None
+    return filtered
+
+
 # ============================================================================
 # User LLM Model Configuration Endpoints
 # ============================================================================
@@ -101,7 +116,7 @@ async def get_user_own_llm_model_configs(
                 config_id=config.config_id,
                 name=config.name,
                 model_type=config.model_type,
-                config=config.config,
+                config=_filter_api_key_from_config(config.config),
                 user_id=config.user_id,
                 group_id=config.group_id,
                 is_default=config.is_default,
@@ -146,7 +161,7 @@ async def get_user_default_llm_model_config(
             config_id=config.config_id,
             name=config.name,
             model_type=config.model_type,
-            config=config.config,
+            config=_filter_api_key_from_config(config.config),
             user_id=config.user_id,
             group_id=config.group_id,
             is_default=config.is_default,
@@ -213,7 +228,7 @@ async def create_user_llm_model_config(
             config_id=new_config.config_id,
             name=new_config.name,
             model_type=new_config.model_type,
-            config=new_config.config,
+            config=_filter_api_key_from_config(new_config.config),
             user_id=new_config.user_id,
             group_id=new_config.group_id,
             is_default=new_config.is_default,
@@ -273,7 +288,7 @@ async def update_user_llm_model_config(
             config_id=updated_config.config_id,
             name=updated_config.name,
             model_type=updated_config.model_type,
-            config=updated_config.config,
+            config=_filter_api_key_from_config(updated_config.config),
             user_id=updated_config.user_id,
             group_id=updated_config.group_id,
             is_default=updated_config.is_default,
@@ -362,7 +377,7 @@ async def set_user_default_llm_model_config(
             config_id=config.config_id,
             name=config.name,
             model_type=config.model_type,
-            config=config.config,
+            config=_filter_api_key_from_config(config.config),
             user_id=config.user_id,
             group_id=config.group_id,
             is_default=config.is_default,
@@ -406,7 +421,7 @@ async def get_group_llm_model_configs(
                 config_id=config.config_id,
                 name=config.name,
                 model_type=config.model_type,
-                config=config.config,
+                config=_filter_api_key_from_config(config.config),
                 user_id=config.user_id,
                 group_id=config.group_id,
                 is_default=config.is_default,
@@ -468,7 +483,7 @@ async def get_group_default_llm_model_config(
             config_id=config.config_id,
             name=config.name,
             model_type=config.model_type,
-            config=config.config,
+            config=_filter_api_key_from_config(config.config),
             user_id=config.user_id,
             group_id=config.group_id,
             is_default=config.is_default,
@@ -535,7 +550,7 @@ async def create_group_llm_model_config(
             config_id=new_config.config_id,
             name=new_config.name,
             model_type=new_config.model_type,
-            config=new_config.config,
+            config=_filter_api_key_from_config(new_config.config),
             user_id=new_config.user_id,
             group_id=new_config.group_id,
             is_default=new_config.is_default,
@@ -595,7 +610,7 @@ async def update_group_llm_model_config(
             config_id=updated_config.config_id,
             name=updated_config.name,
             model_type=updated_config.model_type,
-            config=updated_config.config,
+            config=_filter_api_key_from_config(updated_config.config),
             user_id=updated_config.user_id,
             group_id=updated_config.group_id,
             is_default=updated_config.is_default,
@@ -684,7 +699,7 @@ async def set_group_default_llm_model_config(
             config_id=config.config_id,
             name=config.name,
             model_type=config.model_type,
-            config=config.config,
+            config=_filter_api_key_from_config(config.config),
             user_id=config.user_id,
             group_id=config.group_id,
             is_default=config.is_default,