fix: Resolve containerd dependency issues and OpenAPI JSON parsing

Fixes containerd v2 compatibility issues and OpenAPI JSON endpoint:

Containerd Dependencies:
- Downgraded from containerd/v2 v2.0.0-rc.4 to containerd v1.7.27
- Updated imports from v2 paths to v1 paths in sandbox package
- Fixed client initialization and method calls for v1 API
- Updated test files to use containerd v1 types and methods
- Resolved errdefs.FromGRPC undefined errors

OpenAPI JSON Endpoint:
- Fixed YAML parsing issues caused by angle brackets in descriptions
- Updated JSON endpoint to use embedded spec for reliability
- Removed problematic angle brackets from OpenAPI descriptions
- Both YAML and JSON endpoints now work correctly

Files modified:
- go.mod - Updated containerd dependency to v1.7.27
- internal/sandbox/containerd.go - Updated to v1 API
- internal/sandbox/containerd_hardening_test.go - Updated imports
- tests/security/hardened_container_test.go - Updated imports
- internal/web/api.go - Fixed JSON endpoint parsing
- docs/api/openapi.yaml - Removed angle brackets from descriptions

Build Status: ✅ Working
OpenAPI Endpoints: ✅ Working
Lima Compatibility: ✅ Working