feat(embed,ui04): E01 v2 contract skeleton — displayMode/scrollSpeed/reactionsEnabled, v2 loader entry and fixed 195x280 shell

- contracts: EmbedSlotSettings optional v2 fields (carousel default) + SlotSettingsPayload; gen + redocly green
- api: DTO validation + normalization full-set (cn manage + ov public projection share normalizeStoredSettings)
- embed-loader: params v2 parse/merge/url family, loader-v2.js fixed shell (border/radius/#10161E/safe-area, resize ignored, stack gap 12), dual-artifact build+sync; v1 source frozen
- viewer: EmbedPage v=2 branch, EmbedStream (viewport/track/real anchors/collapse/empty), stream.ts pure fns, i18n zh/en
- admin: types + utils (create default vertical-stream, clampScrollSpeed, v1/v2 snippet selection)
- tests: loader 36 (+9 v2), viewer 222, admin 82, api unit 51, v1 embed e2e 20, v2 E01 gate 2 (195x280 desktop+mobile cross-origin, no footer)

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

eslint.config.js

@@ -19,8 +19,9 @@ module.exports = tseslint.config(
       // 生成产物不参与 lint（契约生成类型已提交入库，改动随 `pnpm gen` 审查）
       '**/generated/',
       // embed-loader 发布产物拷贝（viewer publicDir 携带，源在 packages/embed-loader
-      // ——esbuild minify 输出不适用 lint；P4b Task 3 起 viewer lint 曾因此红）
-      'apps/viewer/public/embed/v1/',
+      // ——esbuild minify 输出不适用 lint；P4b Task 3 起 viewer lint 曾因此红；
+      // UI-04 起 v1/v2 双产物同规则忽略）
+      'apps/viewer/public/embed/',
       // Playwright 运行产物
       '**/playwright-report/',
       '**/test-results/',