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

backend/src/db.ts

@@ -0,0 +1,29 @@
+import { Pool, PoolConfig } from "pg";
+import { config } from "./config";
+
+const poolConfig: PoolConfig = {
+  host: config.db.host,
+  port: config.db.port,
+  database: config.db.database,
+  user: config.db.user,
+  password: config.db.password,
+  max: 10,
+  idleTimeoutMillis: 30_000,
+  connectionTimeoutMillis: 5_000,
+};
+
+export const pool = new Pool(poolConfig);
+
+pool.on("error", (err) => {
+  console.error("[db] Unexpected pool error:", err.message);
+});
+
+export async function checkDbConnection(): Promise<boolean> {
+  try {
+    const client = await pool.connect();
+    client.release();
+    return true;
+  } catch {
+    return false;
+  }
+}