feat(server): скелет Go-сервера с healthz, readyz и api/v1/meta

- internal/config: конфигурация из env с валидацией и дефолтами (§5.1, §9.1)
- internal/httpx: middleware (request id, slog-логи, recover, security-заголовки),
  единый формат ошибок §8.5 и лимит тела запроса
- internal/database: SQLite WAL + busy_timeout + foreign_keys, один writer
  и пул чтения, goose-миграции embedded, PRAGMA optimize по расписанию
- internal/meta: полезная нагрузка /api/v1/meta (версия, фичи, лимиты)
- internal/server: маршруты, SPA-раздача собранного клиента, OpenAPI 3.1
- cmd/glchat: точка входа с graceful shutdown и JSON-логами
- тесты: конфиг, миграции и идемпотентность, HTTP-эндпоинты, статика, 404/405

cmd/glchat/main.go

@@ -0,0 +1,130 @@
+package main
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"log/slog"
+	"net/http"
+	"os"
+	"os/signal"
+	"syscall"
+
+	"glchat/internal/config"
+	"glchat/internal/database"
+	"glchat/internal/server"
+)
+
+// Build metadata is injected with -ldflags "-X main.version=... -X main.commit=... -X main.buildDate=...".
+var (
+	version   = "dev"
+	commit    = "none"
+	buildDate = "unknown"
+)
+
+func main() {
+	if err := run(); err != nil {
+		slog.Error("glchat exited with error", slog.Any("error", err))
+		os.Exit(1)
+	}
+}
+
+func run() error {
+	if v := os.Getenv("APP_VERSION"); v != "" {
+		version = v
+	}
+	if c := os.Getenv("APP_COMMIT"); c != "" {
+		commit = c
+	}
+	if b := os.Getenv("APP_BUILD_DATE"); b != "" {
+		buildDate = b
+	}
+
+	cfg, err := config.Load()
+	if err != nil {
+		return fmt.Errorf("load configuration: %w", err)
+	}
+	cfg.Version = version
+	cfg.Commit = commit
+	cfg.BuildDate = buildDate
+
+	logger := newLogger(cfg)
+	slog.SetDefault(logger)
+
+	ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGTERM)
+	defer stop()
+
+	db, err := database.Open(ctx, database.Options{
+		Path:      cfg.DatabasePath,
+		ReadPool:  cfg.ReadPoolSize,
+		CacheSize: cfg.SQLiteCache,
+		MmapSize:  cfg.SQLiteMmap,
+		Migrate:   true,
+	})
+	if err != nil {
+		return fmt.Errorf("open database: %w", err)
+	}
+	defer func() {
+		if err := db.Close(); err != nil {
+			logger.Error("close database", slog.Any("error", err))
+		}
+	}()
+
+	schemaVersion, err := db.SchemaVersion(ctx)
+	if err != nil {
+		return err
+	}
+	journalMode, err := db.JournalMode(ctx)
+	if err != nil {
+		return err
+	}
+	logger.Info("database ready",
+		slog.String("path", db.Path()),
+		slog.Int64("schema_version", schemaVersion),
+		slog.String("journal_mode", journalMode),
+	)
+
+	stopMaintenance := db.RunMaintenance(ctx, logger, cfg.Maintenance)
+	defer stopMaintenance()
+
+	srv := server.New(cfg, db, logger)
+	errCh := make(chan error, 1)
+	go func() {
+		logger.Info("http server listening",
+			slog.String("addr", cfg.ListenAddr),
+			slog.String("version", cfg.Version),
+			slog.String("domain", cfg.Domain),
+		)
+		if err := srv.ListenAndServe(); err != nil && !errors.Is(err, http.ErrServerClosed) {
+			errCh <- err
+		}
+	}()
+
+	select {
+	case err := <-errCh:
+		return fmt.Errorf("http server: %w", err)
+	case <-ctx.Done():
+		logger.Info("shutdown requested")
+	}
+
+	shutdownCtx, cancel := context.WithTimeout(context.Background(), cfg.ShutdownTTL)
+	defer cancel()
+	if err := srv.Shutdown(shutdownCtx); err != nil {
+		return fmt.Errorf("graceful shutdown: %w", err)
+	}
+	return nil
+}
+
+func newLogger(cfg config.Config) *slog.Logger {
+	opts := &slog.HandlerOptions{Level: slog.Level(cfg.LogLevelNumeric())}
+	var handler slog.Handler
+	if cfg.LogFormat == "text" {
+		handler = slog.NewTextHandler(os.Stdout, opts)
+	} else {
+		handler = slog.NewJSONHandler(os.Stdout, opts)
+	}
+	return slog.New(handler).With(
+		slog.String("service", "glchat"),
+		slog.String("version", cfg.Version),
+	)
+}