feat(backend): implement REST API for races calendar

Express + TypeScript backend with PostgreSQL: CRUD endpoints for /races (GET list with year/month filters, GET by id, POST, PATCH, DELETE), health/readiness probes, SQL migration runner, seed script with upsert from CSV, camelCase/snake_case mapper, CORS, env validation, docker-compose, and API docs for frontend.

Made-with: Cursor

.env.example

@@ -0,0 +1,18 @@
+# ─── PostgreSQL ───────────────────────────────────────────────
+DB_HOST=localhost
+DB_PORT=5432
+DB_NAME=calendar_run
+DB_USER=calendar_user
+DB_PASSWORD=calendar_pass
+
+# ─── Backend API ──────────────────────────────────────────────
+# Port the API server listens on
+API_PORT=3001
+
+# ─── CORS ─────────────────────────────────────────────────────
+# Allowed origin for the frontend (Vite dev server default)
+CORS_ORIGIN=http://localhost:5173
+
+# ─── Frontend (Vite) ─────────────────────────────────────────
+# Public URL of the API, used in SPA code via import.meta.env
+VITE_API_BASE_URL=http://localhost:3001