feat: stabilize API startup and lifecycle management

- Refactor server initialization to separate concerns and improve error handling.
- Implement centralized environment validation using Zod.
- Introduce database, Redis, and queue lifecycle management.
- Add health check endpoints for liveness and readiness.
- Enhance error handling middleware for better response structure.
- Implement rate limiting for API endpoints.
- Add request ID middleware for traceability.
- Create Sequelize CLI configuration and baseline migration for schema management.
- Establish CI workflow with Gitea for testing and syntax checks.
- Document foundational changes and migration strategy in PHASE_0_FOUNDATION_STABILIZATION.md.
- Add Docker Compose configuration for local development and testing.
- Implement unit and integration tests for critical functionality.

app/config/database.lifecycle.js

@@ -0,0 +1,9 @@
+const db = require("../models");
+
+const initializeDatabase = async () => db.sequelize.authenticate();
+const checkDatabase = async () => {
+  try { await db.sequelize.authenticate(); return true; } catch (_error) { return false; }
+};
+const closeDatabase = async () => db.sequelize.close();
+
+module.exports = { initializeDatabase, checkDatabase, closeDatabase };