Posture checks stored in backend

[javuto]

Summary

• Added environment-scoped Posture configuration under the existing Configuration area, visible only when posture is enabled and the user can manage the environment.
• Restored the Schedule tab’s Add posture checks picker for adding profile-based posture checks with a selected interval.
• Added Posture tab editing for scheduled posture checks, including query name, query SQL, interval, platform, snapshot, and associated profile.
• Persisted posture profile association in schedule entries via profile_id, while keeping evaluation logic out of stored config.
• Added DB-backed posture check defaults/customization plumbing for names, query names, queries, descriptions, scores/weights, enabled state, and related metadata.
• Updated posture scoring/profile loading to use configurable check metadata where applicable.
• Added regression tests for posture schedule merging, profile metadata, environment Posture tab visibility, editing, and picker behavior.

Validation

• cd frontend && npm test -- EnvConfigPage.test.tsx postureSchedule.test.ts
• cd frontend && npm run check
• git diff --check
• GOCACHE=/tmp/osctrl-gocache go test ./pkg/posture ./cmd/api/handlers ./cmd/api ./cmd/tls/handlers ./cmd/cli
• make openapi-check