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/db/models/__init__.py

@@ -23,6 +23,7 @@ from .privileges import Privilege
 from .computes import Compute
 from .images import Image
 from .pools import Resource, ResourcePool
+from .llm_model_configs import LLMModelConfig
 from .templates import (
     Template,
     CloudTemplate,

gns3server/db/models/llm_model_configs.py

@@ -0,0 +1,72 @@
+#!/usr/bin/env python
+#
+# Copyright (C) 2026 GNS3 Technologies Inc.
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+from sqlalchemy import Column, Boolean, ForeignKey, CheckConstraint, UniqueConstraint, Index
+from sqlalchemy.dialects.postgresql import JSONB
+from sqlalchemy.orm import relationship
+
+from .base import BaseTable, generate_uuid, GUID
+
+import logging
+
+log = logging.getLogger(__name__)
+
+
+class LLMModelConfig(BaseTable):
+    """
+    LLM model configuration for users and user groups.
+    Supports inheritance: users can inherit configs from their groups.
+    """
+
+    __tablename__ = "llm_model_configs"
+
+    config_id = Column(GUID, primary_key=True, default=generate_uuid)
+    config = Column(JSONB, nullable=False)  # All config fields including name, provider, etc.
+    user_id = Column(GUID, ForeignKey("users.user_id", ondelete="CASCADE"), nullable=True)
+    group_id = Column(GUID, ForeignKey("user_groups.user_group_id", ondelete="CASCADE"), nullable=True)
+    is_default = Column(Boolean, default=False, nullable=False)
+
+    # Relationships
+    user = relationship("User", backref="llm_model_configs")
+    group = relationship("UserGroup", backref="llm_model_configs")
+
+    # Constraints
+    __table_args__ = (
+        # Ensure a config belongs to either a user or a group, not both
+        CheckConstraint(
+            "(user_id IS NOT NULL AND group_id IS NULL) OR "
+            "(user_id IS NULL AND group_id IS NOT NULL)",
+            name="single_owner_check"
+        ),
+        # Each user can have at most one default config
+        UniqueConstraint("user_id", "is_default", name="unique_user_default",
+                         deferrable=True, initially="deferred",
+                         postgresql_where="is_default = TRUE AND user_id IS NOT NULL"),
+        # Each group can have at most one default config
+        UniqueConstraint("group_id", "is_default", name="unique_group_default",
+                         deferrable=True, initially="deferred",
+                         postgresql_where="is_default = TRUE AND group_id IS NOT NULL"),
+        # Indexes for efficient queries
+        Index("idx_llm_model_configs_user_id", "user_id"),
+        Index("idx_llm_model_configs_group_id", "group_id"),
+        Index("idx_llm_model_configs_config", "config", postgresql_using="gin"),
+    )
+
+    def __repr__(self):
+        config_name = self.config.get("name", "unnamed") if self.config else "unnamed"
+        owner = f"user_{self.user_id}" if self.user_id else f"group_{self.group_id}"
+        return f"<LLMModelConfig {config_name} for {owner} (default={self.is_default})>"