v0.6.3-beta: Migration UX & Auth Visibility Hotfix

[DeepZone]

Motivation

• Existing SQLite databases from pre-v0.6 installs can be missing Alembic state and columns (e.g. created_by_user_id), causing raw SQL errors when saving checks.
• The system status endpoint needs to reliably report migration state so operators know when to run alembic upgrade head before using checks.
• The UI lacked clear auth visibility (who is logged in) and a visible logout action which reduced operational clarity.
• Documentation and troubleshooting for the migration failure must be improved so operators can fix stale schemas safely.

Description

• Hardened migration reporting in backend/app/core/system_status.py by returning schema_version, migration_head, migration_status and optional migration_message, and treating missing alembic_version with existing tables as behind without raising internal exceptions.
• Added operational_warnings to build_system_status when the database schema is not up_to_date and bumped the backend system version to v0.6.3-beta.
• Made check storage resilient by catching sqlalchemy.exc.OperationalError in backend/app/api/routes_checks.py and returning a clear HTTP 503 with migration instructions when the DB is missing created_by_user_id.
• Frontend: store getMe() as currentUser, show username and role in the Layout, add a visible Logout button and logout() API call, display migration-warning banners in Dashboard and System views, and present a friendly message when the backend indicates migrations are required.
• Docs and release notes: added troubleshooting steps for table checks has no column named created_by_user_id to docs/operations/database-migrations.md and appended v0.6.3-beta release notes; bumped versions in backend and frontend metadata.
• Tests: added backend smoke tests that assert migration_status warnings are surfaced and that the check-store path maps the missing-column OperationalError to a migration-related HTTP 503.

Testing

• Ran backend smoke tests: pytest -q backend/tests/test_api_smoke.py and all tests passed (21 passed).
• Built the frontend: npm --prefix frontend run build and the production build completed successfully.
• New/modified backend tests exercising migration-warning and OperationalError handling were executed as part of the test run and passed.

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Codex Task