feat: add groups management API

- GET /auth/groups - list groups with search/pagination
- POST /auth/groups/sync-from-authentik - bulk sync from Authentik
- Group model and database migration

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

pyproject.toml

@@ -1,6 +1,6 @@
 [project]
 name = "core-api"
-version = "1.4.6"
+version = "1.5.0"
 description = "Core Code API - Infrastructure management and tools API"
 readme = "README.md"
 requires-python = ">=3.12"