feat: 接入形态图库与 Seedream 生图操作

展示已有主图、候选图和失败记录，支持单图及批量生成、主图选择。
补充正式 ID 校验、费用确认、图片加载占位和回归测试。
依赖后端 eac8dc3 的项目形态图库只读接口。

src/features/projects/ProjectLayout.vue

@@ -1,7 +1,7 @@
 <script setup lang="ts">
 import { computed, provide } from 'vue'
 import { useRoute } from 'vue-router'
-import { ArrowLeft, RefreshCw, FileText, Layers, Camera, LoaderCircle } from '@lucide/vue'
+import { ArrowLeft, RefreshCw, FileText, Layers, Camera, Images, LoaderCircle } from '@lucide/vue'
 import { StatusBadge } from '../../components/ui'
 import { projectContextKey, useProjectData } from './context'
 import { getOperation } from '../workflows/operations'
@@ -45,6 +45,9 @@ const operation = computed(() => getOperation(id.value))
             <RouterLink :to="`/projects/${id}/breakdown`"
                 ><Layers :size="17" />剧本拆解<span class="nav-code">breakdown</span></RouterLink
             >
+            <RouterLink :to="`/projects/${id}/subject-images`"
+                ><Images :size="17" />形态图片<span class="nav-code">subject-image</span></RouterLink
+            >
             <RouterLink :to="`/projects/${id}/storyboard`"
                 ><Camera :size="17" />分镜设计<span class="nav-code">storyboard</span></RouterLink
             >