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>

packages/embed-loader/package.json

@@ -3,10 +3,10 @@
   "version": "1.0.0",
   "private": true,
   "type": "module",
-  "description": "PhotoLive embeddable widget loader (versioned artifact /embed/v1/loader.js served by viewer static; handwritten zero-dependency JS, bundled+minified via esbuild)",
-  "//": "发布物即 dist/v1/loader.js 文件本身（viewer publicDir 携带，不走 npm）——故 private。src/params.js 是 loader 与单测共用的唯一参数源，esbuild 打包时内联。无 TS：typecheck 任务不存在即被 turbo 干净跳过，lint 由根 flat config 覆盖 .js。",
+  "description": "PhotoLive embeddable widget loader (versioned artifacts /embed/v1 + /embed/v2 served by viewer static; handwritten zero-dependency JS, bundled+minified via esbuild)",
+  "//": "发布物即 dist/{v1,v2}/loader.js 文件本身（viewer publicDir 携带，不走 npm）——故 private。src/params.js 是 loader 与单测共用的唯一参数源，esbuild 打包时内联。v1（carousel）源码冻结不动；v2（UI-04 vertical-stream）独立入口 loader-v2.js。无 TS：typecheck 任务不存在即被 turbo 干净跳过，lint 由根 flat config 覆盖 .js。",
   "scripts": {
-    "build": "esbuild src/loader.js --bundle --minify --format=iife --target=es2018 --outfile=dist/v1/loader.js",
+    "build": "esbuild src/loader.js --bundle --minify --format=iife --target=es2018 --outfile=dist/v1/loader.js && esbuild src/loader-v2.js --bundle --minify --format=iife --target=es2018 --outfile=dist/v2/loader.js",
     "sync": "node sync-to-viewer.js",
     "test": "vitest run",
     "lint": "eslint ."