feat: добавить Image Gateway с кешем Souin

- добавлена сборка Caddy с Souin, Otter и NutsDB

- добавлена конфигурация dev, prod и test Docker Compose

- настроено кеширование через Otter L1 и NutsDB L2

- добавлены e2e-тесты Bun для кеша, restart и purge

- добавлена документация по запуску, API кеша и тестам

tests/e2e/cache-prime.test.js

@@ -0,0 +1,29 @@
+import { describe, expect, test } from "bun:test";
+import {
+  expectHit,
+  expectStored,
+  listKeys,
+  purgeAll,
+  requestImage,
+  waitForReady,
+} from "./helpers.js";
+
+describe("cache prime", () => {
+  test("stores responses in NutsDB and serves hot hits from Otter", async () => {
+    await waitForReady();
+    await purgeAll();
+
+    const miss = await requestImage(103);
+    expect(miss.status).toBe(200);
+    expectStored(miss.cacheStatus);
+
+    const hit = await requestImage(103);
+    expect(hit.status).toBe(200);
+    expectHit(hit.cacheStatus, "OTTER");
+
+    const keys = await listKeys();
+    expect(keys.some((key) => key.includes("/unsafe/resize:fit:103"))).toBe(
+      true,
+    );
+  });
+});