feat(models): 期1 模特库地基 — Model 顶级实体 + 模特库页 + 审核范围扩展

后端:
- 新增 Model(模特)团队级实体:形象图+三视图+声线(声线尾期),官方模板标签,软删
- Asset.Category 枚举一次加全(model_portrait/tri_view/voice/model_tryon/platform_kit/free_create/storyboard),逐期接线
- 送审范围 person → REVIEW_CATEGORIES{person,tri_view,storyboard}(review.py + adminpanel 队列),图片趴不送审;当前行为不变(forward-compat)
- /api/models/ ModelLibraryViewSet:本团队∪官方模板、官方/我的 tab、真人上传、软删(官方不可删)、跨团队资产引用防越权
- backfill_models 命令把历史成套模特(kind=model + 项目流命名配对)归集成 Model,dry-run 默认

前端:
- 左菜单新增「模特库」顶级入口(person 图标)+ 路由 /models
- 模特库页:全部/官方模板/我的模特 tab + 真人上传 + 模特卡(形象图+三视图缩略+官方标签),仅用 design token

测试:assets 10/10 绿;tsc+build 全绿;无头走查 0 console error(全部5/官方3/我的2,官方标签达标)
基线既有 7 失败(ai/projects provider mock 漂移)零新增

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

core/frontend/src/components/app-shell.tsx

@@ -190,6 +190,7 @@ type NavDef = { id: string; page: Page; label: string; icon: string; badge?: num
 const NAV: NavDef[] = [
   { id: "dashboard", page: "dashboard", label: "工作台", icon: "dashboard" },
   { id: "products", page: "products", label: "商品库", icon: "package" },
+  { id: "models", page: "models", label: "模特库", icon: "model" },
   { id: "projects", page: "projects", label: "视频项目", icon: "clapperboard" },
   { id: "asset-factory", page: "assetFactory", label: "图片生成", icon: "sparkles" },
   { id: "library", page: "library", label: "资产库", icon: "library" },
@@ -204,6 +205,7 @@ const PAGE_TO_NAV: Partial<Record<Page, Page>> = {
   products: "products",
   productDetail: "products",
   productCreateUpload: "products",
+  models: "models",
   projects: "projects",
   projectWizard: "projects",
   pipeline: "projects",