refactor: extract Pydantic schemas into schemas/ subpackages

Extract inline Pydantic models from 9 API routers into dedicated
schema modules under schemas/:

- schemas/tool/tool_type.py — ToolTypeCreate, ToolTypeUpdate, etc.
- schemas/tool/tool_instance.py — CreateInstanceRequest, StartInstanceRequest
- schemas/config/config_profile.py — ConfigProfileCreate, ConfigProfileUpdate,
  ConfigProfileResponse, DefaultProfilesUpdate, ValidateGitUrlRequest, etc.
- schemas/system/health.py — DatabaseHealth, DiskHealth, HealthResponse, etc.
- schemas/user/user.py — UserProfileResponse, UserProfileUpdate
- schemas/user/user_config.py — UserConfigResponse, UserConfigUpdate
- schemas/project/project.py — ProjectCreate, ProjectUpdate, etc.
- schemas/project/ssh_key.py — SSHKeyCreate, SSHKeyResponse, etc.
- schemas/project/git_repository.py — GitRepositoryCreate, etc.

API routers now import from src.schemas.* instead of defining inline.
Net change: -548 lines across 16 files.

Quality gates: py_compile passed, ruff passed on all 18 files.

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

@@ -1 +1,18 @@
-"""Tool module."""
+"""Tool schemas module."""
+
+from src.schemas.tool.tool_instance import CreateInstanceRequest, StartInstanceRequest
+from src.schemas.tool.tool_type import (
+    ToolTypeCreate,
+    ToolTypeResponse,
+    ToolTypeUpdate,
+    ToolTypeValidateRequest,
+)
+
+__all__ = [
+    "CreateInstanceRequest",
+    "StartInstanceRequest",
+    "ToolTypeCreate",
+    "ToolTypeResponse",
+    "ToolTypeUpdate",
+    "ToolTypeValidateRequest",
+]