Phase 2: Backend refactor with full CRUD API, expanded schema, and JWT auth

Summary:
Database:

• Expand schema with incident_update, incident_service, maintenance, and maintenance_service tables
• Add ordering and timestamp columns to existing tables

Backend:

• Add full CRUD endpoints for services, incidents, and maintenance
• Add incident lifecycle (create → update → resolve) with update tracking
• Add JWT authentication middleware for admin/write operations
• Add start/dev scripts to package.json
• Remove unused Sequelize dependency

API:

• New RESTful routes (/api/services, /api/incidents, /api/maintenances)
• Legacy endpoints preserved for backward compatibility
• Public GET endpoints, authenticated POST/PUT/DELETE

Reviewers: ieli

Reviewed By: ieli

Differential Revision: https://devcentral.nasqueron.org/D3963