feat: 支持 UserPromptSubmit 事件，将 prompt 存入 MySQL

- 新增 db.go：MySQL 连接管理、自动建表、兼容旧表 ALTER
- handler.go：处理 UserPromptSubmit，从 cwd 提取项目名称
- main.go：可选初始化 MySQL，优雅关闭释放连接
- config.go：新增 MYSQL_DSN 配置项
- 表结构：session_id + project_name + prompt + created_at

main.go

@@ -1,25 +1,71 @@
 package main
 
 import (
+	"context"
 	"log"
 	"net/http"
+	"os"
+	"os/signal"
+	"syscall"
+	"time"
 )
 
 func main() {
 	config := LoadConfig()
 
-	handler := NewHookHandler(config)
+	// 可选初始化 MySQL
+	var db *PromptDB
+	if config.MySQLDSN != "" {
+		var err error
+		db, err = NewPromptDB(config.MySQLDSN)
+		if err != nil {
+			log.Fatalf("failed to init mysql: %v", err)
+		}
+		log.Println("mysql prompt recording enabled")
+	} else {
+		log.Println("mysql not configured, prompt recording disabled")
+	}
 
-	http.HandleFunc("/hooks", handler.HandleHook)
-	http.HandleFunc("/health", func(w http.ResponseWriter, r *http.Request) {
+	handler := NewHookHandler(config, db)
+
+	mux := http.NewServeMux()
+	mux.HandleFunc("/hooks", handler.HandleHook)
+	mux.HandleFunc("/health", func(w http.ResponseWriter, r *http.Request) {
 		w.WriteHeader(http.StatusOK)
 		w.Write([]byte(`{"status":"ok"}`))
 	})
 
+	srv := &http.Server{
+		Addr:         config.Port,
+		Handler:      mux,
+		ReadTimeout:  10 * time.Second,
+		WriteTimeout: 10 * time.Second,
+		IdleTimeout:  60 * time.Second,
+	}
+
+	// 优雅关闭
+	go func() {
+		sigCh := make(chan os.Signal, 1)
+		signal.Notify(sigCh, syscall.SIGINT, syscall.SIGTERM)
+		<-sigCh
+		log.Println("shutting down...")
+
+		ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+		defer cancel()
+
+		if err := srv.Shutdown(ctx); err != nil {
+			log.Printf("server shutdown error: %v", err)
+		}
+		if db != nil {
+			db.Close()
+		}
+	}()
+
 	log.Printf("cc-hook service starting on %s", config.Port)
 	log.Printf("gotify endpoint: %s", config.GotifyURL)
 
-	if err := http.ListenAndServe(config.Port, nil); err != nil {
+	if err := srv.ListenAndServe(); err != http.ErrServerClosed {
 		log.Fatalf("server failed: %v", err)
 	}
+	log.Println("server stopped")
 }