feat(pay): switch checkout counter to SPA redirect + JSON API

- redirect `/pay/checkout-counter/:trade_id` to `/cashier/:trade_id`
- add `/pay/checkout-counter-resp/:trade_id` for checkout JSON payload
- remove embedded `static` release and keep `www` as the web bundle source
- regenerate PWA/www assets and move chain icons to `/www/images/chains`

src/controller/comm/pay_controller.go

@@ -1,11 +1,8 @@
 package comm
 
 import (
-	"html/template"
 	"net/http"
-	"path/filepath"
 
-	"github.com/GMWalletApp/epusdt/config"
 	"github.com/GMWalletApp/epusdt/model/response"
 	"github.com/GMWalletApp/epusdt/model/service"
 	"github.com/labstack/echo/v4"
@@ -13,12 +10,12 @@ import (
 
 // CheckoutCounter 收银台
 // @Summary      Checkout counter page
-// @Description  Render the payment checkout counter HTML page for a given trade
+// @Description  Render the payment checkout counter JSON response for a given trade
 // @Tags         Payment
-// @Produce      html
+// @Produce      json
 // @Param        trade_id path string true "Trade ID"
-// @Success      200 {string} string "HTML page"
-// @Router       /pay/checkout-counter/{trade_id} [get]
+// @Success      200 {object} response.CheckoutCounterResponse
+// @Router       /pay/checkout-counter-resp/{trade_id} [get]
 func (c *BaseCommController) CheckoutCounter(ctx echo.Context) (err error) {
 	tradeId := ctx.Param("trade_id")
 	resp, err := service.GetCheckoutCounterByTradeId(tradeId)
@@ -26,22 +23,13 @@ func (c *BaseCommController) CheckoutCounter(ctx echo.Context) (err error) {
 		if err == service.ErrOrder {
 			// Unknown trade id: render the page with empty payload
 			// (client side shows a friendly "order not found" screen).
-			tmpl, tmplErr := template.ParseFiles(filepath.Join(config.StaticFilePath, "index.html"))
-			if tmplErr != nil {
-				return ctx.String(http.StatusInternalServerError, tmplErr.Error())
-			}
-			ctx.Response().Status = http.StatusNotFound
 			emptyResp := response.CheckoutCounterResponse{}
-			return tmpl.Execute(ctx.Response(), emptyResp)
+			return c.SucJson(ctx, emptyResp)
 		}
 		return ctx.String(http.StatusInternalServerError, err.Error())
 	}
-	tmpl, err := template.ParseFiles(filepath.Join(config.StaticFilePath, "index.html"))
-	if err != nil {
-		return ctx.String(http.StatusInternalServerError, err.Error())
-	}
 
-	return tmpl.Execute(ctx.Response(), resp)
+	return c.SucJson(ctx, resp)
 }
 
 // CheckStatus 支付状态检测