feat: 完成 DOCX R4 元素级视觉门禁

建立 Chromium、Word 与 WPS 的可编辑内容、段落几何、页眉页脚、封面、媒体和逐页视觉比较链路。

支持封面独立分节、正文页码重启、主题页边距与横向纸张，并将自然分页差异降为诊断项。

修正代码块内边距和折叠表格单元格边框映射，14 套主题生产矩阵与六组布局视觉矩阵通过。

apps/server/package.json

@@ -10,6 +10,7 @@
     "test": "vitest run",
     "typecheck": "tsc -p tsconfig.json --noEmit --pretty false",
     "verify:docx-http": "node scripts/verify-docx-http.mjs",
+    "verify:docx-r4-matrix": "node scripts/verify-docx-r4-matrix.mjs",
     "verify:docx-theme-styles": "node scripts/verify-docx-theme-styles.mjs"
   },
   "dependencies": {
@@ -18,6 +19,7 @@
     "@md-to-pdf/docx-engine": "0.1.0",
     "@md-to-pdf/docx-theme-engine": "0.1.0",
     "@md-to-pdf/renderer": "0.1.0",
+    "fflate": "0.8.3",
     "fastify": "^5.6.2",
     "playwright": "1.62.0"
   },