feat: русский UI, версии в футере, даты и устойчивость загрузки API

- API: дата старта всегда YYYY-MM-DD; фронт: parseRaceDate без двойного T00:00:00
- GET /health с version из package.json; Vite define __FRONTEND_VERSION__
- Футер с версиями клиента/сервера (BEM), сетка app-shell на три ряда
- AbortController для карточки старта; ретраи GET при 502–504 и понятные ошибки шлюза
- Русские подписи навигации/страниц, lang=ru, без английских фраз в интерфейсе

frontend/src/api/errors.ts

@@ -42,7 +42,26 @@ function normalizeApiCode(value: string | undefined): ApiErrorCode {
   return "unknown_error";
 }
 
+function isGatewayStatus(status: number): boolean {
+  return status === 502 || status === 503 || status === 504;
+}
+
+function hasStructuredApiError(payload: unknown): payload is ApiErrorPayload {
+  if (payload === null || typeof payload !== "object" || Array.isArray(payload)) {
+    return false;
+  }
+  return typeof (payload as ApiErrorPayload).error === "string";
+}
+
 export function toApiError(status: number, payload: unknown): ApiError {
+  if (isGatewayStatus(status) && !hasStructuredApiError(payload)) {
+    return new ApiError({
+      code: "network_error",
+      status,
+      message: "Сервер временно недоступен. Попробуйте обновить страницу.",
+    });
+  }
+
   const maybePayload = payload as ApiErrorPayload;
   const code = normalizeApiCode(maybePayload?.error);
   const details = Array.isArray(maybePayload?.details)

frontend/src/api/health.ts

@@ -0,0 +1,10 @@
+import { requestJson } from "./http";
+
+export type HealthResponse = {
+  status: string;
+  version: string;
+};
+
+export async function getHealth(init?: RequestInit): Promise<HealthResponse> {
+  return requestJson<HealthResponse>("/health", init);
+}

frontend/src/api/http.ts

@@ -20,36 +20,68 @@ async function parseResponseBody(response: Response): Promise<unknown> {
   }
 }
 
-export async function requestJson<T>(path: string, init?: RequestInit): Promise<T> {
-  try {
-    const response = await fetch(buildUrl(path), {
-      ...init,
-      headers: {
-        "Content-Type": "application/json",
-        ...(init?.headers ?? {}),
-      },
-    });
+const GATEWAY_RETRY_STATUSES = new Set([502, 503, 504]);
 
-    if (response.status === 204) {
-      return undefined as T;
-    }
-
-    const payload = await parseResponseBody(response);
-
-    if (!response.ok) {
-      throw toApiError(response.status, payload);
-    }
-
-    return payload as T;
-  } catch (error) {
-    if (error instanceof ApiError) {
-      throw error;
-    }
-
-    throw new ApiError({
-      code: "network_error",
-      status: null,
-      message: "Не удалось связаться с сервером.",
-    });
-  }
+function delay(ms: number): Promise<void> {
+  return new Promise((resolve) => {
+    setTimeout(resolve, ms);
+  });
+}
+
+export async function requestJson<T>(path: string, init?: RequestInit): Promise<T> {
+  const method = (init?.method ?? "GET").toUpperCase();
+  const idempotent = method === "GET" || method === "HEAD";
+  const maxAttempts = idempotent ? 3 : 1;
+
+  for (let attempt = 1; attempt <= maxAttempts; attempt += 1) {
+    try {
+      const response = await fetch(buildUrl(path), {
+        ...init,
+        headers: {
+          "Content-Type": "application/json",
+          ...(init?.headers ?? {}),
+        },
+      });
+
+      if (response.status === 204) {
+        return undefined as T;
+      }
+
+      const payload = await parseResponseBody(response);
+
+      if (!response.ok) {
+        const retryable = idempotent && GATEWAY_RETRY_STATUSES.has(response.status) && attempt < maxAttempts;
+        if (retryable) {
+          await delay(80 * attempt);
+          continue;
+        }
+        throw toApiError(response.status, payload);
+      }
+
+      return payload as T;
+    } catch (error) {
+      if (error instanceof ApiError) {
+        throw error;
+      }
+      if (error instanceof DOMException && error.name === "AbortError") {
+        throw error;
+      }
+      const retryable = idempotent && attempt < maxAttempts;
+      if (retryable) {
+        await delay(80 * attempt);
+        continue;
+      }
+      throw new ApiError({
+        code: "network_error",
+        status: null,
+        message: "Не удалось связаться с сервером.",
+      });
+    }
+  }
+
+  throw new ApiError({
+    code: "network_error",
+    status: null,
+    message: "Не удалось связаться с сервером.",
+  });
 }

frontend/src/api/index.ts

@@ -1,3 +1,5 @@
 export type { CreateRacePayload, Race, RacesQuery, RaceStatus, UpdateRacePayload } from "./types";
 export { ApiError, getApiErrorMessage } from "./errors";
+export type { HealthResponse } from "./health";
+export { getHealth } from "./health";
 export { getRaceById, getRaces, createRace, updateRace, deleteRace } from "./races";

frontend/src/api/races.ts

@@ -77,8 +77,8 @@ function buildRacesQuery(query?: RacesQuery): string {
   return serialized ? `?${serialized}` : "";
 }
 
-export async function getRaces(query?: RacesQuery): Promise<Race[]> {
-  const response = await requestJson<unknown[]>(`/races${buildRacesQuery(query)}`);
+export async function getRaces(query?: RacesQuery, init?: RequestInit): Promise<Race[]> {
+  const response = await requestJson<unknown[]>(`/races${buildRacesQuery(query)}`, init);
   if (!Array.isArray(response)) {
     throw new ApiError({
       code: "unknown_error",
@@ -90,8 +90,8 @@ export async function getRaces(query?: RacesQuery): Promise<Race[]> {
   return response.map(normalizeRace);
 }
 
-export async function getRaceById(id: string): Promise<Race> {
-  return normalizeRace(await requestJson<unknown>(`/races/${id}`));
+export async function getRaceById(id: string, init?: RequestInit): Promise<Race> {
+  return normalizeRace(await requestJson<unknown>(`/races/${id}`, init));
 }
 
 export async function createRace(payload: CreateRacePayload): Promise<Race> {