#639 Epic: Platform Bootstrap & Tenant Lifecycle

Parent epic for self-bootstrapping Highway platform. On fresh deployment, Highway bootstraps itself using its own workflow engine. No manual CLI or scripts needed after docker compose up. Components: - System tenants: _platform, platform, demo, test - Internal tools: internal.tenant.*, internal.platform.*, internal.health.* - System workflows: _system.platform.bootstrap, _system.tenant.onboard, etc. - Platform API for tenant management - Health monitoring workflows Child issues: #641-#652