feat(publish): require cover image for WeChat Official Account

WeChat 公众号在管理员/运营者授权发布场景下需要 2.35:1 封面，
新增共享 publishPlatformRequiresCover 校验并同步前端封面要求与文案，
避免在调度与即时发布两条路径上重复维护平台名单。

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

server/internal/tenant/app/media_service.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"crypto/rand"
 	"encoding/hex"
+	"strings"
 	"time"
 
 	"github.com/jackc/pgx/v5/pgxpool"
@@ -136,13 +137,22 @@ func (s *MediaService) listArticlePublishRecords(ctx context.Context, tenantID,
 
 func publishBatchRequiresCover(accounts []platformAccountSeed) bool {
 	for _, account := range accounts {
-		if account.PlatformID == "baijiahao" || account.PlatformID == "dongchedi" {
+		if publishPlatformRequiresCover(account.PlatformID) {
 			return true
 		}
 	}
 	return false
 }
 
+func publishPlatformRequiresCover(platformID string) bool {
+	switch strings.TrimSpace(platformID) {
+	case "weixin_gzh", "baijiahao", "dongchedi":
+		return true
+	default:
+		return false
+	}
+}
+
 func pointerStringValue(value *string) string {
 	if value == nil {
 		return ""

server/internal/tenant/app/publish_job_service.go

@@ -162,7 +162,7 @@ func (s *PublishJobService) Create(ctx context.Context, actor auth.Actor, req Cr
 		accountSeeds = append(accountSeeds, *target.accountSeed)
 	}
 	if publishBatchRequiresCover(accountSeeds) && strings.TrimSpace(pointerStringValue(articleMeta.CoverAssetURL)) == "" {
-		return nil, response.ErrBadRequest(40044, "publish_cover_required", "baijiahao publishing requires a cover image")
+		return nil, response.ErrBadRequest(40044, "publish_cover_required", "selected publishing platform requires a cover image")
 	}
 
 	publishBatchID, publishRecordIDs, err := createPublishBatchRecords(

server/internal/tenant/app/publish_platforms_test.go

@@ -0,0 +1,30 @@
+package app
+
+import "testing"
+
+func TestPublishPlatformRequiresCover(t *testing.T) {
+	t.Parallel()
+
+	for _, platformID := range []string{"weixin_gzh", "baijiahao", "dongchedi"} {
+		if !publishPlatformRequiresCover(platformID) {
+			t.Fatalf("publishPlatformRequiresCover(%q) = false, want true", platformID)
+		}
+	}
+
+	if publishPlatformRequiresCover("zhihu") {
+		t.Fatal("publishPlatformRequiresCover(\"zhihu\") = true, want false")
+	}
+}
+
+func TestPublishCoverRequirementCallersIncludeWeixinGzh(t *testing.T) {
+	t.Parallel()
+
+	accounts := []platformAccountSeed{{PlatformID: "weixin_gzh"}}
+	if !publishBatchRequiresCover(accounts) {
+		t.Fatal("publishBatchRequiresCover() = false for weixin_gzh, want true")
+	}
+
+	if !schedulePublishPlatformsRequireCover([]string{"weixin_gzh"}) {
+		t.Fatal("schedulePublishPlatformsRequireCover() = false for weixin_gzh, want true")
+	}
+}

server/internal/tenant/app/schedule_task_service.go

@@ -564,8 +564,7 @@ func (s *ScheduleTaskService) loadPublishAccountPlatformIDs(ctx context.Context,
 
 func schedulePublishPlatformsRequireCover(platformIDs []string) bool {
 	for _, platformID := range platformIDs {
-		switch strings.TrimSpace(platformID) {
-		case "baijiahao", "dongchedi":
+		if publishPlatformRequiresCover(platformID) {
 			return true
 		}
 	}