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>

deploy/nginx/default.conf.template

@@ -0,0 +1,48 @@
+# Шаблон обрабатывается envsubst при старте контейнера nginx (переменные: API_UPSTREAM).
+# TLS терминируется здесь или на внешнем прокси — см. docs/deployment.md.
+
+upstream pipu_api {
+    server ${API_UPSTREAM};
+    keepalive 16;
+}
+
+server {
+    listen 80;
+    server_name _;
+
+    root /usr/share/nginx/html;
+    client_max_body_size 16m;
+
+    gzip on;
+    gzip_types text/css application/javascript application/json image/svg+xml;
+
+    location /api/ {
+        proxy_pass http://pipu_api;
+        proxy_http_version 1.1;
+        proxy_set_header Connection "";
+        proxy_set_header Host $host;
+        proxy_set_header X-Real-IP $remote_addr;
+        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+        proxy_set_header X-Forwarded-Proto $scheme;
+    }
+
+    location = /healthz { proxy_pass http://pipu_api; }
+    location = /readyz  { proxy_pass http://pipu_api; }
+
+    # Аудио и обложки отдаёт nginx по заголовку X-Accel-Redirect от api (docs/playback.md).
+    location /_internal/library/ { internal; alias /library/;          sendfile on; aio threads; }
+    location /_internal/cache/   { internal; alias /cache/transcode/;  sendfile on; }
+    location /_internal/covers/  { internal; alias /cache/covers/;     expires 30d; }
+    location /_internal/uploads/ { internal; alias /uploads/;          sendfile on; }
+
+    location /assets/ {
+        expires 1y;
+        add_header Cache-Control "public, immutable";
+        try_files $uri =404;
+    }
+
+    location / {
+        add_header Cache-Control "no-cache";
+        try_files $uri $uri/ /index.html;
+    }
+}