feat: M0 monorepo skeleton with services, clients, deploy and CI

- api/openapi.yaml: contract with /healthz, /readyz, /api/v1/server-info
- services/api (Go): api with oapi-codegen strict server, goose migrations,
  readiness checks for Postgres/Redis; storage-agent stub with internal token
- services/recommender (Python, uv): FastAPI health/readiness/internal status,
  `pipu-rec serve` and `pipu-rec analyze` entrypoints
- packages: generated api-client, core (server URL + server check),
  i18n (ru/en + dictionary check), design-tokens (CSS vars + TS from tokens.json)
- apps/web: Vite + React shell showing server status, language switch
- apps/mobile: Expo (SDK 53) Android app with server connect screen
- deploy: Dockerfiles, compose (prod + dev), nginx template, install/update scripts
- .gitea/workflows: ci.yml and tag-based release.yml (images, signed APK, release)
- scripts/version.mjs: version and Android versionCode from git tag
- tests/fixtures/music/generate.sh: synthetic test library via ffmpeg
- docs: versionCode formula, OpenAPI 3.0.3, dev instructions in README

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

packages/i18n/src/index.ts

@@ -0,0 +1,47 @@
+import i18next, { type i18n as I18n } from 'i18next';
+
+import enCommon from '../locales/en/common.json';
+import ruCommon from '../locales/ru/common.json';
+
+/** Поддерживаемые языки. Новый язык = папка в locales/ + строка здесь. */
+export const SUPPORTED_LOCALES = ['ru', 'en'] as const;
+export type Locale = (typeof SUPPORTED_LOCALES)[number];
+export const DEFAULT_LOCALE: Locale = 'en';
+
+export const resources = {
+  ru: { common: ruCommon },
+  en: { common: enCommon },
+} as const;
+
+declare module 'i18next' {
+  interface CustomTypeOptions {
+    defaultNS: 'common';
+    resources: (typeof resources)['ru'];
+  }
+}
+
+/** Выбирает поддерживаемый язык из списка предпочтений (navigator.languages, настройки ОС). */
+export function pickLocale(preferred: readonly string[]): Locale {
+  for (const tag of preferred) {
+    const base = tag.toLowerCase().split('-')[0];
+    const match = SUPPORTED_LOCALES.find((l) => l === base);
+    if (match) return match;
+  }
+  return DEFAULT_LOCALE;
+}
+
+/** Создаёт и инициализирует экземпляр i18next. */
+export async function createI18n(locale: Locale): Promise<I18n> {
+  const instance = i18next.createInstance();
+  await instance.init({
+    lng: locale,
+    fallbackLng: DEFAULT_LOCALE,
+    supportedLngs: [...SUPPORTED_LOCALES],
+    defaultNS: 'common',
+    ns: ['common'],
+    resources,
+    interpolation: { escapeValue: false },
+    returnNull: false,
+  });
+  return instance;
+}