fix: 数据持久化到/app/data目录，简化部署配置

- 配置文件和SQLite数据库存储在/app/data
- Docker volume持久化数据
- 无需预设环境变量，安装向导自动配置

backend/internal/router/install/install.go

@@ -80,9 +80,9 @@ func handleTestDatabase(c *gin.Context) {
 	}
 
 	if req.DbType == "sqlite" {
-		dbPath := "verification_platform.db"
-		absPath, _ := filepath.Abs(dbPath)
-		testDB, err := gorm.Open(sqlite.Open(absPath), &gorm.Config{
+		dataDir := config.GetDataDir()
+		dbPath := filepath.Join(dataDir, "verification_platform.db")
+		testDB, err := gorm.Open(sqlite.Open(dbPath), &gorm.Config{
 			Logger: logger.Default.LogMode(logger.Silent),
 		})
 		if err != nil {
@@ -167,9 +167,9 @@ func handleSetup(c *gin.Context) {
 	var err error
 
 	if req.DbType == "sqlite" {
-		dbPath := "verification_platform.db"
-		absPath, _ := filepath.Abs(dbPath)
-		newDB, err = gorm.Open(sqlite.Open(absPath), &gorm.Config{
+		dataDir := config.GetDataDir()
+		dbPath := filepath.Join(dataDir, "verification_platform.db")
+		newDB, err = gorm.Open(sqlite.Open(dbPath), &gorm.Config{
 			Logger:                                   logger.Default.LogMode(logger.Silent),
 			DisableForeignKeyConstraintWhenMigrating: true,
 		})
@@ -241,6 +241,11 @@ func handleSetup(c *gin.Context) {
 }
 
 func checkConfigFile() bool {
+	dataDir := config.GetDataDir()
+	configPath := filepath.Join(dataDir, "config.yaml")
+	if _, err := os.Stat(configPath); err == nil {
+		return true
+	}
 	paths := []string{"config.yaml", "./config/config.yaml"}
 	for _, p := range paths {
 		if _, err := os.Stat(p); err == nil {
@@ -338,7 +343,9 @@ func generateConfigFile(dbType string, req SetupRequest, jwtSecret string) strin
 }
 
 func saveConfigFile(content string) error {
-	file, err := os.Create("config.yaml")
+	dataDir := config.GetDataDir()
+	configPath := filepath.Join(dataDir, "config.yaml")
+	file, err := os.Create(configPath)
 	if err != nil {
 		return err
 	}