Add new DB schemas: companies, agent_api_keys, approvals, cost_events,
heartbeat_runs, issue_comments. Add corresponding shared types and
validators. Update existing schemas (agents, goals, issues, projects)
with new fields for company association, budgets, and richer metadata.
Generate initial Drizzle migration. Update seed data.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
