feat(api): add LLM model configurations endpoint and schemas

- Introduce new API route `/access` for managing LLM model configurations
- Add LLMModelConfig model to database models
- Include comprehensive schemas for LLM model config CRUD operations
- Register new router with tags for LLM Model Configurations

gns3server/schemas/__init__.py

@@ -30,6 +30,15 @@ from .controller.gns3vm import GNS3VM
 from .controller.nodes import NodeCreate, NodeUpdate, NodeDuplicate, NodeCapture, Node
 from .controller.projects import ProjectCreate, ProjectUpdate, ProjectDuplicate, Project, ProjectFile, ProjectCompression
 from .controller.users import UserCreate, UserUpdate, LoggedInUserUpdate, User, Credentials, UserGroupCreate, UserGroupUpdate, UserGroup
+from .controller.llm_model_configs import (
+    LLMModelConfigData,
+    LLMModelConfigCreate,
+    LLMModelConfigUpdate,
+    LLMModelConfigResponse,
+    LLMModelConfigListResponse,
+    LLMModelConfigWithSource,
+    LLMModelConfigInheritedResponse
+)
 from .controller.rbac import RoleCreate, RoleUpdate, Role, Privilege, ACECreate, ACEUpdate, ACE
 from .controller.pools import Resource, ResourceCreate, ResourcePoolCreate, ResourcePoolUpdate, ResourcePool
 from .controller.tokens import Token