Phase 0+1+2 续: 项目骨架 + 配置 + 日志 + 存储层

Phase 0 (项目骨架):
- main.go 改为最小骨架 (config + logging + gin + /healthz + 优雅退出)
- internal/{config,logging,storage,cluster,...}/ 目录占位

Phase 1 (配置 + 日志):
- internal/config: env 解析 + 必填校验 + token 隐藏的 String()
- internal/logging: slog multi-handler 双输出 (终端 text + 主文件 JSON)
  + StartToolCall per-tool 独立文件 (0600), tools 目录 0700

Phase 2 续 (存储层):
- internal/cluster: 16 字段 Cluster struct (AuthPassword json:"-")
- internal/storage: modernc.org/sqlite 接入, WAL 模式, schema 自动迁移
- ClusterRepo CRUD: Create/Get/List/Update/Delete + ErrNotFound
  + AuthPassword 空字符串 = 保留旧密码 (核心约定)
- 7 个单元测试全绿 (:memory: DB)
- created_at/updated_at 改纳秒精度, 消除 List 测试的 sleep 特殊 case

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

internal/logging/logger.go

@@ -0,0 +1,135 @@
+package logging
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"log/slog"
+	"os"
+	"path/filepath"
+	"strings"
+	"sync"
+)
+
+// Config configures the application logger.
+type Config struct {
+	Level    string // "debug"|"info"|"warn"|"error"
+	Dir      string // e.g. "./data/logs"
+	Format   string // "text"|"json" — controls terminal output; files are always JSON
+	LogToStd bool   // true: enable terminal output
+}
+
+// ToolCallLogger records the lifecycle of a single tool call.
+type ToolCallLogger interface {
+	WithResult(result any)
+	WithError(err error)
+	End()
+}
+
+// logDir is shared with StartToolCall so the per-tool-call logger knows where
+// to create files. It is set by New and read by StartToolCall.
+var (
+	logDir   string
+	logDirMu sync.RWMutex
+)
+
+func parseLevel(s string) slog.Level {
+	switch strings.ToLower(s) {
+	case "debug":
+		return slog.LevelDebug
+	case "warn", "warning":
+		return slog.LevelWarn
+	case "error":
+		return slog.LevelError
+	default:
+		return slog.LevelInfo
+	}
+}
+
+// multiHandler fans out records to multiple underlying handlers.
+type multiHandler struct {
+	handlers []slog.Handler
+}
+
+func (m *multiHandler) Enabled(ctx context.Context, l slog.Level) bool {
+	for _, h := range m.handlers {
+		if h.Enabled(ctx, l) {
+			return true
+		}
+	}
+	return false
+}
+
+func (m *multiHandler) Handle(ctx context.Context, r slog.Record) error {
+	var errs []error
+	for _, h := range m.handlers {
+		if h.Enabled(ctx, r.Level) {
+			if err := h.Handle(ctx, r); err != nil {
+				errs = append(errs, err)
+			}
+		}
+	}
+	return errors.Join(errs...)
+}
+
+func (m *multiHandler) WithAttrs(attrs []slog.Attr) slog.Handler {
+	handlers := make([]slog.Handler, len(m.handlers))
+	for i, h := range m.handlers {
+		handlers[i] = h.WithAttrs(attrs)
+	}
+	return &multiHandler{handlers: handlers}
+}
+
+func (m *multiHandler) WithGroup(name string) slog.Handler {
+	handlers := make([]slog.Handler, len(m.handlers))
+	for i, h := range m.handlers {
+		handlers[i] = h.WithGroup(name)
+	}
+	return &multiHandler{handlers: handlers}
+}
+
+// New creates the main application logger and a shutdown closure.
+func New(cfg Config) (*slog.Logger, func(), error) {
+	if err := os.MkdirAll(cfg.Dir, 0o755); err != nil {
+		return nil, nil, fmt.Errorf("logging: create log dir: %w", err)
+	}
+
+	toolsDir := filepath.Join(cfg.Dir, "tools")
+	if err := os.MkdirAll(toolsDir, 0o700); err != nil {
+		return nil, nil, fmt.Errorf("logging: create tools log dir: %w", err)
+	}
+
+	logDirMu.Lock()
+	logDir = cfg.Dir
+	logDirMu.Unlock()
+
+	level := parseLevel(cfg.Level)
+	opts := &slog.HandlerOptions{Level: level}
+
+	mainPath := filepath.Join(cfg.Dir, "spark-mcp.log")
+	f, err := os.OpenFile(mainPath, os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0o600)
+	if err != nil {
+		return nil, nil, fmt.Errorf("logging: open main log file: %w", err)
+	}
+
+	fileHandler := slog.NewJSONHandler(f, opts)
+
+	var handler slog.Handler = fileHandler
+	if cfg.LogToStd {
+		var stdHandler slog.Handler
+		switch strings.ToLower(cfg.Format) {
+		case "json":
+			stdHandler = slog.NewJSONHandler(os.Stdout, opts)
+		default:
+			stdHandler = slog.NewTextHandler(os.Stdout, opts)
+		}
+		handler = &multiHandler{handlers: []slog.Handler{fileHandler, stdHandler}}
+	}
+
+	shutdown := func() {
+		_ = f.Close()
+	}
+
+	logger := slog.New(handler).With("component", "main")
+	return logger, shutdown, nil
+}