config: GIN_MODE 改为环境变量配置 + Load() 自动加载 .env

main.go 硬编码 gin.ReleaseMode 改成读 cfg.GinMode（默认 release），
方便生产/调试切换 debug/release/test。Load() 开头先调 loadDotenv
(".env"): 缺文件静默跳过，shell env 优先于 .env，跳过注释/空行/
无 '=' 行并 slog.Warn。仅用标准库，不引新依赖。

验证:
  - go build / go vet / go test 全部通过
  - shell env 覆盖 .env (LISTEN_ADDR=:19090 覆盖 .env 的 :18080)
  - 仅 .env 时正确加载 (监听 18080, GIN_MODE=debug 输出 [GIN-debug])
  - 无 .env 且无 shell env 时清晰报错 ADMIN_TOKENS is not set

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

.env.example

@@ -31,6 +31,9 @@ LOG_LEVEL=info
 # Log format: text (terminal) or json (log file; default: text)
 LOG_FORMAT=text
 
+# Gin mode: debug, release, test (default: release)
+GIN_MODE=release
+
 # Analyzer heuristic thresholds (defaults shown)
 ANALYZER_DATA_SKEW_RATIO=3.0
 ANALYZER_GC_PRESSURE_RATIO=0.1

internal/config/config.go

@@ -2,7 +2,9 @@
 package config
 
 import (
+	"bufio"
 	"fmt"
+	"log/slog"
 	"os"
 	"path/filepath"
 	"strconv"
@@ -23,6 +25,7 @@ type Config struct {
 	LogDir                      string
 	LogLevel                    string
 	LogFormat                   string
+	GinMode                     string
 	AnalyzerDataSkewRatio       float64
 	AnalyzerGCPressureRatio     float64
 	AnalyzerBottleneckShuffleGB float64
@@ -31,6 +34,10 @@ type Config struct {
 // Load reads configuration from environment variables and returns a populated Config.
 // Required variables (ADMIN_TOKENS, AGENT_TOKEN) produce clear errors when missing.
 func Load() (*Config, error) {
+	if err := loadDotenv(".env"); err != nil {
+		return nil, err
+	}
+
 	cfg := &Config{
 		ListenAddr:                  ":8080",
 		DataDir:                     "./data",
@@ -40,6 +47,7 @@ func Load() (*Config, error) {
 		LogDir:                      "./data/logs",
 		LogLevel:                    "info",
 		LogFormat:                   "text",
+		GinMode:                     "release",
 		AnalyzerDataSkewRatio:       3.0,
 		AnalyzerGCPressureRatio:     0.1,
 		AnalyzerBottleneckShuffleGB: 50.0,
@@ -75,6 +83,7 @@ func Load() (*Config, error) {
 	cfg.LogDir = envString("LOG_DIR", cfg.LogDir)
 	cfg.LogLevel = envString("LOG_LEVEL", cfg.LogLevel)
 	cfg.LogFormat = envString("LOG_FORMAT", cfg.LogFormat)
+	cfg.GinMode = envString("GIN_MODE", cfg.GinMode)
 
 	cfg.AnalyzerDataSkewRatio, err = parseFloat64("ANALYZER_DATA_SKEW_RATIO", cfg.AnalyzerDataSkewRatio)
 	if err != nil {
@@ -97,6 +106,9 @@ func Load() (*Config, error) {
 	if err := validateLogFormat(cfg.LogFormat); err != nil {
 		return nil, err
 	}
+	if err := validateGinMode(cfg.GinMode); err != nil {
+		return nil, err
+	}
 
 	cfg.SQLitePath = filepath.Join(cfg.DataDir, "spark-mcp.db")
 
@@ -192,6 +204,70 @@ func validateLogFormat(format string) error {
 	return fmt.Errorf("config: invalid LOG_FORMAT %q, want text/json", format)
 }
 
+func validateGinMode(mode string) error {
+	switch mode {
+	case "debug", "release", "test":
+		return nil
+	}
+	return fmt.Errorf("config: invalid GIN_MODE %q, want debug/release/test", mode)
+}
+
+// loadDotenv reads KEY=VALUE pairs from path and sets them via os.Setenv only
+// when the variable is not already defined. Missing files are ignored.
+func loadDotenv(path string) error {
+	f, err := os.Open(path)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return nil
+		}
+		return fmt.Errorf("config: failed to open %s: %w", path, err)
+	}
+	defer f.Close()
+
+	scanner := bufio.NewScanner(f)
+	for scanner.Scan() {
+		line := strings.TrimSpace(scanner.Text())
+		if line == "" || strings.HasPrefix(line, "#") {
+			continue
+		}
+
+		eq := strings.Index(line, "=")
+		if eq < 0 {
+			slog.Warn("config: .env line without '=', skipping", "line", line)
+			continue
+		}
+
+		key := strings.TrimSpace(line[:eq])
+		value := strings.TrimSpace(line[eq+1:])
+		value = dequote(value)
+
+		if key == "" {
+			slog.Warn("config: .env line with empty key, skipping", "line", line)
+			continue
+		}
+
+		if os.Getenv(key) == "" {
+			if err := os.Setenv(key, value); err != nil {
+				return fmt.Errorf("config: failed to set env %s: %w", key, err)
+			}
+		}
+	}
+
+	if err := scanner.Err(); err != nil {
+		return fmt.Errorf("config: failed to read %s: %w", path, err)
+	}
+	return nil
+}
+
+func dequote(s string) string {
+	if len(s) >= 2 {
+		if (s[0] == '"' && s[len(s)-1] == '"') || (s[0] == '\'' && s[len(s)-1] == '\'') {
+			return s[1 : len(s)-1]
+		}
+	}
+	return s
+}
+
 // String returns a human-readable representation of the configuration.
 // Sensitive values (AdminTokens and AgentToken) are summarized, not printed.
 func (c *Config) String() string {
@@ -206,7 +282,7 @@ func (c *Config) String() string {
 		"ListenAddr=%s DataDir=%s SQLitePath=%s AdminTokens=%s AgentToken=%s "+
 			"HTTPClientTimeout=%s MaxResponseBytes=%d SparkSubmitTimeout=%s "+
 			"LogDir=%s LogLevel=%s LogFormat=%s AnalyzerDataSkewRatio=%.1f "+
-			"AnalyzerGCPressureRatio=%.1f AnalyzerBottleneckShuffleGB=%.1f",
+			"AnalyzerGCPressureRatio=%.1f AnalyzerBottleneckShuffleGB=%.1f GinMode=%s",
 		c.ListenAddr,
 		c.DataDir,
 		c.SQLitePath,
@@ -221,5 +297,6 @@ func (c *Config) String() string {
 		c.AnalyzerDataSkewRatio,
 		c.AnalyzerGCPressureRatio,
 		c.AnalyzerBottleneckShuffleGB,
+		c.GinMode,
 	)
 }

main.go

@@ -65,7 +65,7 @@ func run() error {
 	defer db.Close()
 	logger.Info("storage.open", "path", cfg.SQLitePath)
 
-	gin.SetMode(gin.ReleaseMode)
+	gin.SetMode(cfg.GinMode)
 	r := gin.New()
 	r.Use(gin.Recovery())