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/config/config_profile.py

@@ -1,7 +1,6 @@
 """Config profile request/response schemas."""
 
 import uuid
-from typing import Any
 
 from pydantic import BaseModel, Field, field_validator, model_validator
 
@@ -13,8 +12,8 @@ def _validate_uuid(v: str | None) -> str | None:
         return v
     try:
         uuid.UUID(v)
-    except ValueError:
-        raise ValueError(f"Invalid UUID: {v}")
+    except ValueError as exc:
+        raise ValueError(f"Invalid UUID: {v}") from exc
     return v
 
 
@@ -236,8 +235,8 @@ class ConfigProfileIncludeUpdate(BaseModel):
         for item in v:
             try:
                 uuid.UUID(item)
-            except ValueError:
-                raise ValueError(f"Invalid UUID in includes: {item}")
+            except ValueError as exc:
+                raise ValueError(f"Invalid UUID in includes: {item}") from exc
         return v