feat: add config profiles

- Add ConfigProfile and ConfigProfileInclude data models with migrations
- Implement profile resolver service with ordered includes and merge rules
- Add profile CRUD API with validation, compatibility, and cycle detection
- Add instance API plumbing for profile selection on create/start/restart
- Add resolved profile preview and default resolution APIs
- Add frontend config profile API client and management UI
- Add launch/restart profile selection UI
- Add backend integration and unit tests (31 passing)

OpenSpec: add-config-profiles
Quality gates: ruff, TypeScript compile, 31 tests passing

apps/api/src/auth/session.py

@@ -2,7 +2,7 @@ import hmac
 import hashlib
 import json
 import base64
-from datetime import UTC, datetime, timedelta
+from datetime import datetime, timedelta, timezone
 from typing import Any
 
 from src.config import Settings
@@ -23,7 +23,7 @@ def create_session_cookie(*, settings: Settings, user_id: str) -> str:
     """Create a signed session cookie value."""
     payload = {
         "user_id": user_id,
-        "exp": int((datetime.now(UTC) + timedelta(hours=settings.session_ttl_hours)).timestamp()),
+        "exp": int((datetime.now(timezone.utc) + timedelta(hours=settings.session_ttl_hours)).timestamp()),
     }
     
     header = _base64url_encode(json.dumps({"alg": "HS256", "typ": "session"}).encode())
@@ -65,7 +65,7 @@ def decode_session_cookie(*, settings: Settings, cookie_value: str) -> dict[str,
     payload = json.loads(payload_bytes)
     
     # Check expiry
-    if payload.get("exp", 0) < int(datetime.now(UTC).timestamp()):
+    if payload.get("exp", 0) < int(datetime.now(timezone.utc).timestamp()):
         raise ValueError("session expired")
     
     return payload