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>

services/api/internal/platform/db/db.go

@@ -0,0 +1,42 @@
+// Package db — подключение к PostgreSQL и применение миграций.
+package db
+
+import (
+	"context"
+	"database/sql"
+	"fmt"
+
+	"github.com/jackc/pgx/v5/pgxpool"
+	"github.com/jackc/pgx/v5/stdlib"
+	"github.com/pressly/goose/v3"
+
+	"pipu/api/migrations"
+)
+
+// Connect открывает пул соединений и проверяет доступность БД.
+func Connect(ctx context.Context, url string) (*pgxpool.Pool, error) {
+	pool, err := pgxpool.New(ctx, url)
+	if err != nil {
+		return nil, fmt.Errorf("db: open pool: %w", err)
+	}
+	if err := pool.Ping(ctx); err != nil {
+		pool.Close()
+		return nil, fmt.Errorf("db: ping: %w", err)
+	}
+	return pool, nil
+}
+
+// Migrate применяет встроенные миграции goose.
+func Migrate(ctx context.Context, pool *pgxpool.Pool) error {
+	sqlDB := stdlib.OpenDBFromPool(pool)
+	defer func(d *sql.DB) { _ = d.Close() }(sqlDB)
+
+	provider, err := goose.NewProvider(goose.DialectPostgres, sqlDB, migrations.FS)
+	if err != nil {
+		return fmt.Errorf("db: migrations: %w", err)
+	}
+	if _, err := provider.Up(ctx); err != nil {
+		return fmt.Errorf("db: migrate up: %w", err)
+	}
+	return nil
+}