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/mappers/race.ts

@@ -0,0 +1,88 @@
+/** Row shape returned by PostgreSQL (snake_case). */
+export interface RaceRow {
+  id: string;
+  race_date: string;
+  title: string;
+  distance_km: string;
+  status: string | null;
+  official_url: string | null;
+  start_time: string | null;
+  cluster_schedule: string | null;
+  bib_pickup: string | null;
+  bib_number: string | null;
+  finish_time: string | null;
+  notes: string | null;
+  created_at: string;
+  updated_at: string | null;
+}
+
+/** API shape (camelCase). */
+export interface RaceDto {
+  id: string;
+  date: string;
+  title: string;
+  distanceKm: number;
+  status: string | null;
+  officialUrl: string | null;
+  startTime: string | null;
+  clusterSchedule: string | null;
+  bibPickup: string | null;
+  bibNumber: string | null;
+  finishTime: string | null;
+  notes: string | null;
+  createdAt: string;
+  updatedAt: string | null;
+}
+
+/** Convert a DB row to the API DTO (camelCase). */
+export function rowToDto(row: RaceRow): RaceDto {
+  return {
+    id: row.id,
+    date: row.race_date,
+    title: row.title,
+    distanceKm: parseFloat(row.distance_km),
+    status: row.status,
+    officialUrl: row.official_url,
+    startTime: row.start_time,
+    clusterSchedule: row.cluster_schedule,
+    bibPickup: row.bib_pickup,
+    bibNumber: row.bib_number,
+    finishTime: row.finish_time,
+    notes: row.notes,
+    createdAt: row.created_at,
+    updatedAt: row.updated_at,
+  };
+}
+
+/** Map incoming camelCase body fields to snake_case column names. */
+const FIELD_MAP: Record<string, string> = {
+  date: "race_date",
+  title: "title",
+  distanceKm: "distance_km",
+  status: "status",
+  officialUrl: "official_url",
+  startTime: "start_time",
+  clusterSchedule: "cluster_schedule",
+  bibPickup: "bib_pickup",
+  bibNumber: "bib_number",
+  finishTime: "finish_time",
+  notes: "notes",
+};
+
+/**
+ * Convert a partial camelCase body into { columns, values, placeholders }
+ * suitable for SQL INSERT / UPDATE.
+ */
+export function bodyToColumns(body: Record<string, unknown>) {
+  const columns: string[] = [];
+  const values: unknown[] = [];
+
+  for (const [camel, snake] of Object.entries(FIELD_MAP)) {
+    if (camel in body) {
+      columns.push(snake);
+      values.push(body[camel]);
+    }
+  }
+
+  return { columns, values };
+}