feat(post): add idempotency support for post creation with client request ID

Add client_request_id field to post creation endpoints (CreateVotePost and CreatePostWithSegments).
When provided, the server uses Redis SetNX-based idempotency to prevent duplicate posts
from double-clicks or network retries within a 24-hour TTL. Duplicate requests return
the originally created post; concurrent in-flight requests return 429 "正在发布中，请稍候".

internal/handler/post_handler.go

@@ -5,6 +5,7 @@ import (
 	"errors"
 	"fmt"
 	"log"
+	"net/http"
 	"strconv"
 
 	"github.com/gin-gonic/gin"
@@ -105,13 +106,18 @@ func (h *PostHandler) Create(c *gin.Context) {
 		return
 	}
 
-	post, err := h.postService.Create(c.Request.Context(), userID, req.Title, content, segments, req.Images, req.ChannelID)
+	post, err := h.postService.Create(c.Request.Context(), userID, req.Title, content, segments, req.Images, req.ChannelID, req.ClientRequestID)
 	if err != nil {
 		var moderationErr *service.PostModerationRejectedError
 		if errors.As(err, &moderationErr) {
 			response.BadRequest(c, moderationErr.UserMessage())
 			return
 		}
+		// 幂等命中"进行中"占位：提示客户端稍候，避免重复提交
+		if errors.Is(err, service.ErrDuplicatePostRequest) {
+			response.ErrorWithStatusCode(c, http.StatusTooManyRequests, 429, err.Error())
+			return
+		}
 		response.InternalServerError(c, "failed to create post")
 		return
 	}

internal/handler/vote_handler.go

@@ -47,6 +47,11 @@ func (h *VoteHandler) CreateVotePost(c *gin.Context) {
 			response.BadRequest(c, moderationErr.UserMessage())
 			return
 		}
+		// 幂等命中"进行中"占位：提示客户端稍候，避免重复提交
+		if errors.Is(err, service.ErrDuplicatePostRequest) {
+			response.ErrorWithStatusCode(c, http.StatusTooManyRequests, 429, err.Error())
+			return
+		}
 		response.Error(c, http.StatusBadRequest, err.Error())
 		return
 	}