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/services/config/__init__.py

@@ -0,0 +1 @@
+"""Config module."""

apps/api/src/services/config_profile_resolver.py

@@ -13,7 +13,7 @@ from typing import Any
 from sqlalchemy import select
 from sqlalchemy.ext.asyncio import AsyncSession
 
-from src.models.config_profile import ConfigProfile, ConfigProfileInclude
+from src.models import ConfigProfile, ConfigProfileInclude
 
 logger = logging.getLogger(__name__)
 

apps/api/src/services/file_service.py

@@ -4,7 +4,7 @@ import logging
 import os
 from dataclasses import dataclass
 
-from src.models.workspace import Workspace
+from src.models import Workspace
 
 logger = logging.getLogger(__name__)
 

apps/api/src/services/git/__init__.py

@@ -0,0 +1 @@
+"""Git module."""

apps/api/src/services/git_operations.py

@@ -4,7 +4,7 @@ import asyncio
 import logging
 from dataclasses import dataclass
 
-from src.models.workspace import Workspace
+from src.models import Workspace
 
 logger = logging.getLogger(__name__)
 

apps/api/src/services/health_monitor.py

@@ -10,8 +10,8 @@ from sqlalchemy import select
 from sqlalchemy.ext.asyncio import AsyncSession
 
 from src.database import SessionLocal
-from src.models.health_check import HealthCheck
-from src.models.tool_instance import ToolInstance
+from src.models import HealthCheck
+from src.models import ToolInstance
 from src.services.correlation import get_correlation_id
 from src.services.docker import get_container_status
 from src.services.tunnel import check_tunnel_health

apps/api/src/services/instance/__init__.py

@@ -0,0 +1 @@
+"""Instance module."""

apps/api/src/services/lifecycle_hooks.py

@@ -6,8 +6,8 @@ from datetime import datetime, timezone
 
 from sqlalchemy.ext.asyncio import AsyncSession
 
-from src.models.instance_event import InstanceEvent
-from src.models.tool_instance import ToolInstance
+from src.models import InstanceEvent
+from src.models import ToolInstance
 from src.services.correlation import get_correlation_id
 from src.services.event_bus import InstanceEventBus, InstanceEventPayload
 from src.services.notification_service import notification_service

apps/api/src/services/notification_service.py

@@ -8,7 +8,7 @@ from sqlalchemy import func, select, update
 from sqlalchemy.engine import CursorResult
 from sqlalchemy.ext.asyncio import AsyncSession
 
-from src.models.notification import Notification
+from src.models import Notification
 
 
 class NotificationService:

apps/api/src/services/shared/__init__.py

@@ -0,0 +1 @@
+"""Shared module."""

apps/api/src/services/terminal/__init__.py

@@ -0,0 +1 @@
+"""Terminal module."""

apps/api/src/services/terminal_manager.py

@@ -9,7 +9,7 @@ from fastapi import WebSocket
 from sqlalchemy.dialects.postgresql import insert as pg_insert
 
 from src.database import SessionLocal
-from src.models.terminal_session import TerminalSessionModel
+from src.models import TerminalSessionModel
 from src.services.terminal_session import TerminalSession
 
 logger = logging.getLogger(__name__)

apps/api/src/services/workspace_manager.py

@@ -14,15 +14,15 @@ from typing import TYPE_CHECKING
 
 from sqlalchemy import select
 
-from src.models.workspace import Workspace
+from src.models import Workspace
 from src.services.git_service import GitService
 from src.services.ssh_keys import _get_fernet
 
 if TYPE_CHECKING:
     from sqlalchemy.ext.asyncio import AsyncSession
 
-    from src.models.git_repository import GitRepository
-    from src.models.tool_instance import ToolInstance
+    from src.models import GitRepository
+    from src.models import ToolInstance
 
 logger = logging.getLogger(__name__)
 
@@ -96,7 +96,7 @@ class WorkspaceManager:
         # Load SSH key if repo has one
         ssh_key = None
         if getattr(repo, "ssh_key_id", None) and session is not None:
-            from src.models.ssh_key import SSHKey
+            from src.models import SSHKey
 
             result = await session.execute(
                 select(SSHKey).where(SSHKey.id == repo.ssh_key_id)
@@ -181,8 +181,8 @@ class WorkspaceManager:
         # Load SSH key if repo has one
         ssh_key = None
         if session is not None:
-            from src.models.git_repository import GitRepository
-            from src.models.ssh_key import SSHKey
+            from src.models import GitRepository
+            from src.models import SSHKey
 
             repo = await session.get(GitRepository, workspace.repo_id)
             if repo and getattr(repo, "ssh_key_id", None):
@@ -241,7 +241,7 @@ class WorkspaceManager:
         session: AsyncSession,
     ) -> list[ToolInstance]:
         """Get all tool instances associated with this workspace."""
-        from src.models.tool_instance import ToolInstance
+        from src.models import ToolInstance
 
         result = await session.execute(
             select(ToolInstance).where(ToolInstance.workspace_id == workspace.id)