feat: Go 重写后端，替换 Python FastAPI

用 Go (Gin + GORM + SQLite) 重写整个后端：
- 单二进制部署，不依赖 Python/pip/SDK
- net/http 原生客户端，无 Cloudflare TLS 指纹问题
- 多阶段 Dockerfile：Node 构建前端 + Go 构建后端 + Alpine 运行
- 内存占用从 ~95MB 降至 ~3MB
- 完整保留所有 API 路由、JWT 认证、API Key 权限、审计日志

handlers/transactions.go

@@ -0,0 +1,44 @@
+package handlers
+
+import (
+	"net/http"
+	"strconv"
+
+	"github.com/gin-gonic/gin"
+
+	"airwallex-admin/models"
+	"airwallex-admin/services"
+)
+
+func ListTransactions(c *gin.Context) {
+	pageNum, _ := strconv.Atoi(c.DefaultQuery("page_num", "0"))
+	pageSize, _ := strconv.Atoi(c.DefaultQuery("page_size", "20"))
+	cardID := c.Query("card_id")
+	fromCreatedAt := c.Query("from_created_at")
+	toCreatedAt := c.Query("to_created_at")
+
+	result, err := services.ListTransactions(models.DB, pageNum, pageSize, cardID, fromCreatedAt, toCreatedAt)
+	if err != nil {
+		c.JSON(http.StatusBadRequest, gin.H{"detail": err.Error()})
+		return
+	}
+
+	c.JSON(http.StatusOK, result)
+}
+
+func ListAuthorizations(c *gin.Context) {
+	pageNum, _ := strconv.Atoi(c.DefaultQuery("page_num", "0"))
+	pageSize, _ := strconv.Atoi(c.DefaultQuery("page_size", "20"))
+	cardID := c.Query("card_id")
+	status := c.Query("status")
+	fromCreatedAt := c.Query("from_created_at")
+	toCreatedAt := c.Query("to_created_at")
+
+	result, err := services.ListAuthorizations(models.DB, pageNum, pageSize, cardID, status, fromCreatedAt, toCreatedAt)
+	if err != nil {
+		c.JSON(http.StatusBadRequest, gin.H{"detail": err.Error()})
+		return
+	}
+
+	c.JSON(http.StatusOK, result)
+}