feat: init sproutclaw-web — Go+Gin backend + React frontend

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/internal/handlers/extension_ui.go

@@ -0,0 +1,25 @@
+package handlers
+
+import (
+	"net/http"
+
+	"github.com/gin-gonic/gin"
+	"sproutclaw-web/internal/models"
+	"sproutclaw-web/internal/rpc"
+)
+
+// RegisterExtensionUI registers the extension UI response route.
+func RegisterExtensionUI(r *gin.RouterGroup, piClient *rpc.Client) {
+	r.POST("/extension-ui-response", func(c *gin.Context) {
+		var req models.ExtensionUIResponseRequest
+		if err := c.ShouldBindJSON(&req); err != nil {
+			c.JSON(http.StatusBadRequest, models.ErrorResponse{Error: err.Error()})
+			return
+		}
+		if err := piClient.SendExtensionUIResponse(req.ID, req.Response); err != nil {
+			c.JSON(http.StatusInternalServerError, models.ErrorResponse{Error: err.Error()})
+			return
+		}
+		c.JSON(http.StatusOK, models.OKResponse{OK: true})
+	})
+}