feat: Project maturity improvements, test coverage, cleanups

[gallayl]

🚀 Project Maturity Improvements

Major architecture overhaul moving from MVP to production-ready codebase. Migrates data persistence from filesystem stores to Sequelize/PostgreSQL with a fully normalized schema, applies SOLID principles by extracting focused service classes, and adds real-time entity sync, MCP integration, API token auth, and service state history.

🗄️ Data Layer

• Migrate all persistent models to Sequelize with PostgreSQL
• Normalize schema with proper FK constraints, indexes, and associations
• Add join tables for service prerequisites and dependency links
• Move sessions to PostgreSQL (from in-memory)

🏗️ Backend Architecture

• Extract ProcessRunner, ServiceStatusManager, GitOperationsService, StaleStateReconciler, ServiceEnvResolver from monolithic ProcessManager
• Add DomainError hierarchy with HTTP status code mapping
• Add service state history with event tracking and automatic pruning
• Add MCP server with tools for managing stacks, services, prerequisites, and env vars
• Add bearer token authentication for API access

🎨 Frontend

• Refactor layout into modular components (header, sidebar, breadcrumbs, body)
• Update routing and page components
• Improve form handling patterns

🧪 Testing

• Add withTestInjector and createMockActionContext test helpers
• Increase unit test coverage for REST actions and services
• Improve E2E test reliability