refactor: reorganize models into subpackages

Move models into domain subpackages (max 4 files each):
- models/tool/ — tool_type, tool_instance, tool_definition_manifest
- models/config/ — config_profile
- models/user/ — user, user_config, ssh_key
- models/project/ — project, git_repository, workspace
- models/system/ — health_check, notification, instance_event, terminal_session

models/__init__.py continues to re-export all symbols, so consumers
using 'from src.models import X' are unaffected. Updated direct file
imports across the backend to use the new paths.

Quality gates: py_compile passed, ruff passed.

apps/api/src/models/__init__.py

@@ -1,18 +1,18 @@
 from src.models.base import Base
-from src.models.config_profile import ConfigProfile, ConfigProfileInclude
-from src.models.git_repository import GitRepository
-from src.models.health_check import HealthCheck
-from src.models.instance_event import InstanceEvent
-from src.models.notification import Notification
-from src.models.project import Project
-from src.models.ssh_key import SSHKey
-from src.models.terminal_session import TerminalSessionModel
-from src.models.tool_definition_manifest import ToolDefinitionManifest
-from src.models.tool_instance import ToolInstance
-from src.models.tool_type import ToolType
-from src.models.user import User
-from src.models.user_config import UserConfig
-from src.models.workspace import Workspace
+from src.models.config.config_profile import ConfigProfile, ConfigProfileInclude
+from src.models.project.git_repository import GitRepository
+from src.models.project.project import Project
+from src.models.project.workspace import Workspace
+from src.models.system.health_check import HealthCheck
+from src.models.system.instance_event import InstanceEvent
+from src.models.system.notification import Notification
+from src.models.system.terminal_session import TerminalSessionModel
+from src.models.tool.tool_definition_manifest import ToolDefinitionManifest
+from src.models.tool.tool_instance import ToolInstance
+from src.models.tool.tool_type import ToolType
+from src.models.user.ssh_key import SSHKey
+from src.models.user.user import User
+from src.models.user.user_config import UserConfig
 
 __all__ = [
     "Base",

apps/api/src/models/config/__init__.py

@@ -0,0 +1,5 @@
+"""Config models module."""
+
+from src.models.config.config_profile import ConfigProfile, ConfigProfileInclude
+
+__all__ = ["ConfigProfile", "ConfigProfileInclude"]

apps/api/src/models/config/config_profile.py

@@ -17,7 +17,7 @@ from src.models.base import Base, TimestampMixin, UUIDPrimaryKeyMixin
 
 if TYPE_CHECKING:
     from src.models.project import Project
-    from src.models.tool_type import ToolType
+    from src.models import ToolType
     from src.models.user import User
 
 

apps/api/src/models/project/__init__.py

@@ -0,0 +1,7 @@
+"""Project models module."""
+
+from src.models.project.git_repository import GitRepository
+from src.models.project.project import Project
+from src.models.project.workspace import Workspace
+
+__all__ = ["GitRepository", "Project", "Workspace"]

apps/api/src/models/project/git_repository.py

@@ -10,7 +10,7 @@ from src.models.base import Base, TimestampMixin, UUIDPrimaryKeyMixin
 
 if TYPE_CHECKING:
     from src.models.project import Project
-    from src.models.ssh_key import SSHKey
+    from src.models import SSHKey
     from src.models.user import User
 
 

apps/api/src/models/project/project.py

@@ -8,8 +8,8 @@ from sqlalchemy.orm import Mapped, mapped_column, relationship
 from src.models.base import Base, TimestampMixin, UUIDPrimaryKeyMixin
 
 if TYPE_CHECKING:
-    from src.models.git_repository import GitRepository
-    from src.models.ssh_key import SSHKey
+    from src.models import GitRepository
+    from src.models import SSHKey
     from src.models.user import User
 
 

apps/api/src/models/project/workspace.py

@@ -12,7 +12,7 @@ from sqlalchemy.orm import Mapped, mapped_column, relationship
 from src.models.base import Base, TimestampMixin
 
 if TYPE_CHECKING:
-    from src.models.git_repository import GitRepository
+    from src.models import GitRepository
     from src.models.user import User
 
 

apps/api/src/models/system/__init__.py

@@ -0,0 +1,8 @@
+"""System models module."""
+
+from src.models.system.health_check import HealthCheck
+from src.models.system.instance_event import InstanceEvent
+from src.models.system.notification import Notification
+from src.models.system.terminal_session import TerminalSessionModel
+
+__all__ = ["HealthCheck", "InstanceEvent", "Notification", "TerminalSessionModel"]

apps/api/src/models/tool/__init__.py

@@ -0,0 +1,7 @@
+"""Tool models module."""
+
+from src.models.tool.tool_definition_manifest import ToolDefinitionManifest
+from src.models.tool.tool_instance import ToolInstance
+from src.models.tool.tool_type import ToolType
+
+__all__ = ["ToolDefinitionManifest", "ToolInstance", "ToolType"]

apps/api/src/models/tool/tool_instance.py

@@ -9,12 +9,12 @@ from sqlalchemy.orm import Mapped, mapped_column, relationship
 from src.models.base import Base, TimestampMixin, UUIDPrimaryKeyMixin
 
 if TYPE_CHECKING:
-    from src.models.config_profile import ConfigProfile
-    from src.models.git_repository import GitRepository
+    from src.models import ConfigProfile
+    from src.models import GitRepository
     from src.models.project import Project
-    from src.models.tool_type import ToolType
+    from src.models import ToolType
     from src.models.user import User
-    from src.models.workspace import Workspace
+    from src.models import Workspace
 
 
 class ToolInstance(UUIDPrimaryKeyMixin, TimestampMixin, Base):

apps/api/src/models/tool/tool_type.py

@@ -6,8 +6,7 @@ from sqlalchemy import Uuid as UUID
 from sqlalchemy.orm import Mapped, mapped_column, relationship
 
 from src.models.base import Base, TimestampMixin, UUIDPrimaryKeyMixin
-
-from src.models.tool_definition_manifest import ToolDefinitionManifest
+from src.models.tool.tool_definition_manifest import ToolDefinitionManifest
 
 if TYPE_CHECKING:
     from src.models.user import User

apps/api/src/models/user/__init__.py

@@ -0,0 +1,7 @@
+"""User models module."""
+
+from src.models.user.ssh_key import SSHKey
+from src.models.user.user import User
+from src.models.user.user_config import UserConfig
+
+__all__ = ["SSHKey", "User", "UserConfig"]

apps/api/src/models/user/user.py

@@ -7,8 +7,8 @@ from src.models.base import Base, TimestampMixin, UUIDPrimaryKeyMixin
 
 if TYPE_CHECKING:
     from src.models.project import Project
-    from src.models.ssh_key import SSHKey
-    from src.models.user_config import UserConfig
+    from src.models import SSHKey
+    from src.models import UserConfig
 
 
 class User(UUIDPrimaryKeyMixin, TimestampMixin, Base):